Add v0.34.24 changelog entry and upgrading guidelines (#9746)

Follows from #9734, porting to `main`.

---

#### PR checklist

- [x] Tests written/updated, or no tests needed
- [x] `CHANGELOG_PENDING.md` updated, or no changelog entry needed
- [x] Updated relevant documentation (`docs/`) and code comments, or no
      documentation updates needed

CHANGELOG.md

@@ -2,6 +2,24 @@
 
 Friendly reminder, we have a [bug bounty program](https://hackerone.com/cosmos).
 
+## v0.34.24
+
+*Nov 22, 2022*
+
+Apart from one minor bug fix, this release aims to optimize the output of the
+RPC (both HTTP and WebSocket endpoints). See our [upgrading
+guidelines](./UPGRADING.md#v03424) for more details.
+
+### IMPROVEMENTS
+
+- `[rpc]` [\#9724](https://github.com/tendermint/tendermint/issues/9724) Remove
+  useless whitespace in RPC output (@adizere, @thanethomson)
+
+### BUG FIXES
+
+- `[rpc]` [\#9692](https://github.com/tendermint/tendermint/issues/9692) Remove
+  `Cache-Control` header response from `/check_tx` endpoint (@JayT106)
+
 ## v0.34.23
 
 *Nov 9, 2022*

UPGRADING.md

@@ -41,6 +41,14 @@ Tendermint Core.
   this should have no effect on the wire-level encoding for UTF8-encoded
   strings.
 
+## v0.34.24
+
+Note that in [\#9724](https://github.com/tendermint/tendermint/pull/9724) we
+un-prettified the JSON output (i.e. removed all indentation) of the HTTP and
+WebSocket RPC for performance and subscription stability reasons. We recommend
+using a tool such as [jq](https://github.com/stedolan/jq) to obtain prettified
+output if you rely on that prettified output in some way.
+
 ## v0.34.20
 
 ### Feature: Priority Mempool