tests: fix tst_qqmllanguage::importIncorrectCase() and errors(incorrectCase)

It gives different error message based on the case sensitivity of
the file system on Mac.

Task-number: QTBUG-37622
Change-Id: I567eb4a0b9a413f6eb51683b568f6a6284e6458d
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>