posts: remove unused flag! and approve! methods.

These methods were unused outside of the test suite

app/models/post.rb

@@ -254,18 +254,6 @@ class Post < ApplicationRecord
       !is_active? && uploader != user
     end
 
-    def flag!(reason, is_deletion: false)
-      flag = flags.create(reason: reason, is_deletion: is_deletion, creator: CurrentUser.user)
-
-      if flag.errors.any?
-        raise PostFlag::Error, flag.errors.full_messages.join("; ")
-      end
-    end
-
-    def approve!(approver = CurrentUser.user)
-      approvals.create(user: approver)
-    end
-
     def disapproved_by?(user)
       PostDisapproval.exists?(user_id: user.id, post_id: id)
     end

app/models/post_approval.rb

@@ -29,7 +29,7 @@ class PostApproval < ApplicationRecord
     post.appeals.pending.update!(status: :succeeded)
 
     post.update(approver: user, is_flagged: false, is_pending: false, is_deleted: false)
-    ModAction.log("undeleted post ##{post_id}", :post_undelete) if is_undeletion
+    ModAction.log("undeleted post ##{post_id}", :post_undelete, user) if is_undeletion
 
     post.uploader.upload_limit.update_limit!(is_pending, true)
   end

app/models/post_flag.rb

@@ -1,6 +1,4 @@
 class PostFlag < ApplicationRecord
-  class Error < StandardError; end
-
   module Reasons
     UNAPPROVED = "Unapproved in three days"
     REJECTED = "Unapproved in three days after returning to moderation queue%"