chore: remove "self-moderate" from Moderation Policy (#884)

The term "self-moderate" is probably clear in the context of the
Moderation Policy, but it has become a bit of our project's jargon and
it's not clear that people generally understand what the term means. It
is unnecessary in the Moderation Policy context. I think "edit their
comment" is more clear in the context used here.

Moderation-Policy.md

@@ -195,8 +195,8 @@ Scenario 1:
 
 Scenario 2:
  * A non-Collaborator posts a comment that is against the Code of Conduct.
- * A Collaborator sees the comment and asks the author to self-moderate.
- * The author refuses to self-moderate.
+ * A Collaborator sees the comment and asks the author to edit it.
+ * The author refuses to edit their comment.
  * The Collaborator deletes the comment and posts an issue in the moderation
    repository explaining their actions.