[ticket/11802] replace $browser with $user->browser

PHPBB3-11802
Merge remote-tracking branch 'dhruvgoel92/ticket/11802' into prep-release-3.0.12

* dhruvgoel92/ticket/11802:
  [ticket/11802] replace $browser with $user->browser
Merge branch 'prep-release-3.0.12' into develop-olympus

* prep-release-3.0.12:
  [ticket/11802] replace $browser with $user->browser