Fixed errcheck issues in server/channels/api4/webhook_test.go (#28573)

* errcheck issues fixed

* test bug fixed

* error to NoError

* test error fix

---------

Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>
Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Devin Binnie <52460000+devinbinnie@users.noreply.github.com>

server/.golangci.yml

@@ -84,7 +84,7 @@ issues:
         channels/api4/team_local.go|\
         channels/api4/team_test.go|\
         channels/api4/user_test.go|\
-        channels/api4/webhook_test.go|\
+        channels/api4/websocket_test.go|\
         channels/app/app_test.go|\
         channels/app/authorization_test.go|\
         channels/app/auto_responder_test.go|\