Fixed errcheck issues in server/channels/api4/oauth_test.go (#28645)

Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

server/.golangci.yml

@@ -79,7 +79,6 @@ issues:
         channels/api4/job_test.go|\
         channels/api4/license.go|\
         channels/api4/license_local.go|\
-        channels/api4/oauth_test.go|\
         channels/api4/post_test.go|\
         channels/api4/preference_test.go|\
         channels/api4/reaction_test.go|\