Bump github.com/redis/go-redis/v9 from 9.7.0 to 9.7.3 in /backend

Bumps [github.com/redis/go-redis/v9](https://github.com/redis/go-redis) from 9.7.0 to 9.7.3.
- [Release notes](https://github.com/redis/go-redis/releases)
- [Changelog](https://github.com/redis/go-redis/blob/master/CHANGELOG.md)
- [Commits](https://github.com/redis/go-redis/compare/v9.7.0...v9.7.3)

---
updated-dependencies:
- dependency-name: github.com/redis/go-redis/v9
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

backend/go.mod

@@ -1,7 +1,7 @@
 module github.com/umputun/remark42/backend
 
 go 1.23
-toolchain go1.23.3
+toolchain go1.24.1
 
 require (
 	github.com/Depado/bfchroma/v2 v2.0.0
@@ -60,7 +60,7 @@ require (
 	github.com/klauspost/compress v1.17.11 // indirect
 	github.com/montanaflynn/stats v0.7.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/redis/go-redis/v9 v9.7.0 // indirect
+	github.com/redis/go-redis/v9 v9.7.3 // indirect
 	github.com/rrivera/identicon v0.0.0-20240116195454-d5ba35832c0d // indirect
 	github.com/slack-go/slack v0.15.0 // indirect
 	github.com/xdg-go/pbkdf2 v1.0.0 // indirect