[MM-31404] api4/config: return error when patching PluginSettings.EnableUploads (#16611)

* api4/config: return error when patching PluginSettings.EnableUploads

* reflect review comments

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/config_local.go

@@ -87,9 +87,6 @@ func localPatchConfig(c *Context, w http.ResponseWriter, r *http.Request) {
 		return true
 	}
 
-	// Do not allow plugin uploads to be toggled through the API
-	cfg.PluginSettings.EnableUploads = appCfg.PluginSettings.EnableUploads
-
 	if cfg.MessageExportSettings.EnableExport != nil {
 		c.App.HandleMessageExportConfig(cfg, appCfg)
 	}