testsuite: don't set dummy value for testdir

The test directory is removed during cleanup, if there's an interrupt
that could remove the entire repository.

testsuite/driver/testglobals.py

@@ -440,9 +440,6 @@ class TestOptions:
        # Keep profiling callstacks.
        self.keep_prof_callstacks = False
 
-       # The directory the test is in
-       self.testdir = Path('.')
-
        # Should we redirect stdout and stderr to a single file?
        self.combined_output = False