Revert "Bump Go version to 1.23.6 (#30242)" (#30359)

This reverts commit acbbd4c58d.

server/public/go.mod

@@ -1,8 +1,8 @@
 module github.com/mattermost/mattermost/server/public
 
-go 1.23.0
+go 1.22.0
 
-toolchain go1.23.6
+toolchain go1.22.6
 
 require (
 	github.com/blang/semver/v4 v4.0.0