fix: plugin errcheck issues (#28517)

Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>

server/.golangci.yml

@@ -81,7 +81,6 @@ issues:
         channels/api4/license.go|\
         channels/api4/license_local.go|\
         channels/api4/oauth_test.go|\
-        channels/api4/plugin.go|\
         channels/api4/post_test.go|\
         channels/api4/preference_test.go|\
         channels/api4/reaction_test.go|\