MM-13312 Prevent clobbering of new fields by old plugins. (#10087)

* Prevent clobbering of new fields by old plugins.

* Apply suggestions from code review

Spelling and copy paste error.

Co-Authored-By: crspeller <crspeller@gmail.com>

plugin/interface_generator/main.go

@@ -397,6 +397,8 @@ func removeExcluded(info *PluginInterfaceInfo) *PluginInterfaceInfo {
 			"LoadPluginConfiguration",
 			"ServeHTTP",
 			"FileWillBeUploaded",
+			"MessageWillBePosted",
+			"MessageWillBeUpdated",
 		}
 		for _, exclusion := range excluded {
 			if exclusion == item {