[develop] Remove left over conflict marker from merge 1a31f03
[ticket/12163] Use posts_per_page to calculate current page in viewtopic.php

PHPBB3-12163
Merge pull request #2004 from prototech/ticket/12163

[ticket/12163] Use posts_per_page to calculate current page in viewtopic.php

* prototech/ticket/12163:
  [ticket/12163] Use posts_per_page to calculate current page in viewtopic.php
[prep-release-3.1.0-a3] Update version to 3.1.0-a3
[prep-release-3.1.0-a3] Add migration for 3.1.0-a3
[prep-release-3.1.0-a3] Prepare Changelog
[prep-release-3.1.0-a3] Commit changelog for 3.1.0-a3