Revert "Fix initialism errors (PR-3) (#17062)" (#17202)

This reverts commit ea61458f16. This was causing panic in the plugins because the client and the plugin API changed with this PR

app/plugin_api.go

@@ -537,7 +537,7 @@ func (api *PluginAPI) GetGroupByName(name string) (*model.Group, *model.AppError
 }
 
 func (api *PluginAPI) GetGroupsForUser(userID string) ([]*model.Group, *model.AppError) {
-	return api.app.GetGroupsByUserID(userID)
+	return api.app.GetGroupsByUserId(userID)
 }
 
 func (api *PluginAPI) CreatePost(post *model.Post) (*model.Post, *model.AppError) {