Remove obsolete activerecord patch

The original activerecord patch is no longer needed because the additional functionality it added to 3.2.2  is included in 3.2.12.

3.2.2 only checked if any connection was in use (https://github.com/rails/rails/blob/v3.2.2/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb#L100), but 3.2.12
 (https://github.com/rails/rails/blob/v3.2.12/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb#L107) checks if the current Thread's connection is in use, which matches behavior added by `active_thread_connection?` (https://github.com/rapid7/metasploit-framework/blob/master/lib/msf/core/patches/active_record.rb#L12) in the patch.

3.2.2 only used `@queue.wait` to check for connection timeouts (https://github.com/rails/rails/blob/v3.2.2/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb#L252), but 3.2.12 (https://github.com/rails/rails/blob/v3.2.2/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb#L252) uses `Time.now` similar to how the patch did (https://github.com/rapid7/metasploit-framework/blob/master/lib/msf/core/patches/active_record.rb#L76)