FIX: Do not call :post_edited webhook twice when editing OP (#13112)

When editing the first post for the topic we do two AJAX requests
to two separate controllers in this order:

PUT /t/topic-name
PUT /posts/2489523

This causes two post revisor calls, which end up triggering the
:post_edited DiscourseEvent twice. This is then picked up and sent
as a WebHook event twice. However we do not need to send a :post_edited
webhook event if the first post is being edited and topic_changed is
true from the :post_edited DiscourseEvent, because a second event will
shortly come through for just the post.

See https://meta.discourse.org/t/post-webhook-fires-two-times-on-post-edited-for-first-post-in-a-topic/162408

Continued on from https://github.com/discourse/discourse/pull/10590

lib/post_revisor.rb

@@ -170,7 +170,7 @@ class PostRevisor
 
     @validate_topic = true
     @validate_topic = @opts[:validate_topic] if @opts.has_key?(:validate_topic)
-    @validate_topic = !@opts[:validate_topic] if @opts.has_key?(:skip_validations)
+    @validate_topic = !@opts[:skip_validations] if @opts.has_key?(:skip_validations)
 
     @skip_revision = false
     @skip_revision = @opts[:skip_revision] if @opts.has_key?(:skip_revision)