build(deps): Bump github.com/prometheus/client_golang from 1.7.1 to 1.8.0 (#5515)

Bumps [github.com/prometheus/client_golang](https://github.com/prometheus/client_golang) from 1.7.1 to 1.8.0.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/prometheus/client_golang/releases">github.com/prometheus/client_golang's releases</a>.</em></p>
<blockquote>
<h2>1.8.0 / 2020-10-15</h2>
<ul>
<li>[CHANGE] API client: Use <code>time.Time</code> rather than <code>string</code> for timestamps in <code>RuntimeinfoResult</code>. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/777">#777</a></li>
<li>[FEATURE] Export <code>MetricVec</code> to facilitate implementation of vectors of custom <code>Metric</code> types. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/803">#803</a></li>
<li>[FEATURE API client: Support <code>/status/tsdb</code> endpoint. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/773">#773</a></li>
<li>[ENHANCEMENT] API client: Enable GET fallback on status code 501. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/802">#802</a></li>
<li>[ENHANCEMENT] Remove <code>Metric</code> references after reslicing to free up more memory. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/784">#784</a></li>
</ul>
</blockquote>
</details>
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a href="https://github.com/prometheus/client_golang/blob/master/CHANGELOG.md">github.com/prometheus/client_golang's changelog</a>.</em></p>
<blockquote>
<h2>1.8.0 / 2020-10-15</h2>
<ul>
<li>[CHANGE] API client: Use <code>time.Time</code> rather than <code>string</code> for timestamps in <code>RuntimeinfoResult</code>. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/777">#777</a></li>
<li>[FEATURE] Export <code>MetricVec</code> to facilitate implementation of vectors of custom <code>Metric</code> types. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/803">#803</a></li>
<li>[FEATURE API client: Support <code>/status/tsdb</code> endpoint. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/773">#773</a></li>
<li>[ENHANCEMENT] API client: Enable GET fallback on status code 501. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/802">#802</a></li>
<li>[ENHANCEMENT] Remove <code>Metric</code> references after reslicing to free up more memory. <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/784">#784</a></li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="47cfdc9bb8"><code>47cfdc9</code></a> Merge pull request <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/806">#806</a> from prometheus/beorn7/release</li>
<li><a href="67f573aafe"><code>67f573a</code></a> Cut v1.8.0</li>
<li><a href="ded2474420"><code>ded2474</code></a> Update dependencies</li>
<li><a href="3d1759b4c6"><code>3d1759b</code></a> Run check for unused/missing Go packages only against latest Go version</li>
<li><a href="e6ea98bdda"><code>e6ea98b</code></a> Merge pull request <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/803">#803</a> from prometheus/beorn7/vec</li>
<li><a href="85aa957f63"><code>85aa957</code></a> Export MetricVec (again)</li>
<li><a href="6007b2b5ca"><code>6007b2b</code></a> Merge pull request <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/802">#802</a> from prometheus/beorn7/fallback</li>
<li><a href="64b4a9cf9d"><code>64b4a9c</code></a> API client: Enable fallback on status code 501, too</li>
<li><a href="65c5578b2d"><code>65c5578</code></a> Merge pull request <a href="https://github-redirect.dependabot.com/prometheus/client_golang/issues/800">#800</a> from prometheus/beorn7/doc</li>
<li><a href="b54b73c7b1"><code>b54b73c</code></a> Remove spurious commas from links to the docs site</li>
<li>Additional commits viewable in <a href="https://github.com/prometheus/client_golang/compare/v1.7.1...v1.8.0">compare view</a></li>
</ul>
</details>
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go.mod

@@ -20,7 +20,7 @@ require (
 	github.com/libp2p/go-buffer-pool v0.0.2
 	github.com/minio/highwayhash v1.0.1
 	github.com/pkg/errors v0.9.1
-	github.com/prometheus/client_golang v1.7.1
+	github.com/prometheus/client_golang v1.8.0
 	github.com/rcrowley/go-metrics v0.0.0-20200313005456-10cdbea86bc0
 	github.com/rs/cors v1.7.0
 	github.com/sasha-s/go-deadlock v0.2.0