FIX: TL3 can convert their post to a wiki (#25023)

A bug that allowed TL1 to convert other's posts to wiki.

The issue was introduced in this PR: https://github.com/discourse/discourse/pull/24999/files

The wiki can be created if a user is TL3 and it is their own post - default 3 for setting `SiteSetting.min_trust_to_allow_self_wiki`

In addition, a wiki can be created by staff and TL4 users for any post.

spec/lib/guardian_spec.rb

@@ -3639,8 +3639,6 @@ RSpec.describe Guardian do
   describe "can_wiki?" do
     let(:post) { Fabricate(:post, created_at: 1.minute.ago) }
 
-    before { SiteSetting.edit_wiki_post_allowed_groups = "14" }
-
     it "returns false for regular user" do
       expect(Guardian.new(coding_horror).can_wiki?(post)).to be_falsey
     end