Remove suite included twice in suite.xml

Remove suite included twice in suite.xml
Rename MediaWikiParserTestSuite class to MediaWikiParserTest. This way, it matches its file basename, which makes phpunit not to consider, when loading MediaWikiParserText.php, the ParserUnitTest (coming from ParserHelpers.php require) as a standalone test class, which is what was producing the warning: No tests found in class "ParserUnitTest".

All tests pass for me now:
Tests: 752, Assertions: 3706, Incomplete: 2.

Incomplete tests are testApiListPages() and testWatchRollback()