FEATURE: revert disallowing putting URLs in titles for TL0 users (#13970)

This reverts a part of changes introduced by https://github.com/discourse/discourse/pull/13947

In that PR I:
1. Disallowed topic feature links for TL-0 users
2. Additionally, disallowed just putting any URL in topic titles for TL-0 users

Actually, we don't need the second part. It introduced unnecessary complexity for no good reason. In fact, it tries to do the job that anti-spam plugins (like Akismet plugin) should be doing.

This PR reverts this second change.

lib/guardian.rb

@@ -540,10 +540,6 @@ class Guardian
     !SiteSetting.login_required? || authenticated?
   end
 
-  def can_put_urls_in_topic_title?
-    @user.trust_level >= TrustLevel.levels[:basic]
-  end
-
   def auth_token
     if cookie = request&.cookies[Auth::DefaultCurrentUserProvider::TOKEN_COOKIE]
       UserAuthToken.hash_token(cookie)

lib/post_revisor.rb

@@ -77,12 +77,7 @@ class PostRevisor
   end
 
   track_topic_field(:title) do |topic_changes, attribute|
-    if UrlHelper.contains_url?(attribute) && !topic_changes.guardian.can_put_urls_in_topic_title?
-      topic_changes.topic.errors.add(:base, I18n.t("urls_in_title_require_trust_level"))
-      topic_changes.check_result(false)
-    else
-      track_and_revise topic_changes, :title, attribute
-    end
+    track_and_revise topic_changes, :title, attribute
   end
 
   track_topic_field(:archetype) do |topic_changes, attribute|

lib/url_helper.rb

@@ -65,11 +65,6 @@ class UrlHelper
     Addressable::URI.normalized_encode(uri)
   end
 
-  def self.contains_url?(string)
-    uri_regexp = Discourse::Utils::URI_REGEXP
-    uri_regexp.match?(string)
-  end
-
   def self.rails_route_from_url(url)
     path = URI.parse(encode(url)).path
     Rails.application.routes.recognize_path(path)

lib/validators/urls_in_topic_title_validator.rb

@@ -1,20 +0,0 @@
-# frozen_string_literal: true
-
-class UrlsInTopicTitleValidator < ActiveModel::Validator
-  def validate(record)
-    if UrlHelper.contains_url?(record.title) && !can_put_urls?(record)
-      record.errors.add(:base, error_message)
-    end
-  end
-
-  private
-
-  def can_put_urls?(topic)
-    guardian = Guardian.new(topic.acting_user)
-    guardian.can_put_urls_in_topic_title?
-  end
-
-  def error_message
-    I18n.t("urls_in_title_require_trust_level")
-  end
-end