Fix bootstrap in unit tests

- Remove check for version, that version is already enforced in phpunit.php,
  so there is not point showing a warning for it is useless
- Remove call to MessageCache::destroyInstance(), there is no need for it,
  since $wgMessageCacheType is set in phpunit.php before running Setup.php
- Remove includes of bootstrap.php in LanguageSrTest.php and LanguageUzTest.php

Change-Id: I4b2db6b3e6f001175e1a407c5add2972aade5e60
Merge "Fix bootstrap in unit tests"