Bump Go version to 1.23.6 (#30242)

* Bump Go version to 1.23.6

* Update CodeQL Github action as well

* Use server's Go version for CodeQL action

Co-authored-by: Antonis Stamatiou <stamatiou.antonis@gmail.com>

* Empty commit to trigger CI

* Bump golangci-lint to a version supporting Go 1.23

* Fix golangci-lint warnings

Several rules from gosimple, revive and staticcheck linters were
failing:
- Redefinition of built-in identifiers (max, min, new, recover...)
- Use of printf-like functions with simple strings
- Check for nil slices, when len already takes it into account

---------

Co-authored-by: Antonis Stamatiou <stamatiou.antonis@gmail.com>
Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/notification_push.go

@@ -859,7 +859,7 @@ func (a *App) buildFullPushNotificationMessage(c request.CTX, contentsConfig str
 		}
 	}
 
-	hasFiles := post.FileIds != nil && len(post.FileIds) > 0
+	hasFiles := len(post.FileIds) > 0
 
 	msg.Message = a.getPushNotificationMessage(
 		contentsConfig,