mesonbuild/mtest.py: filter more invalid googletest JUnit4 attributes

googletest 1.12.1 generates new JUnit4 invalid attributes file and
line.

Maybe all gtest "invalid" attributes are actually valid JUnit5
attributes, and maybe schema should be upgraded to JUni5.

Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>

mesonbuild/mtest.py

@@ -775,6 +775,10 @@ def log(self, harness: 'TestHarness', test: 'TestRun') -> None:
                     del case.attrib['result']
                 for case in suite.findall('.//testcase[@timestamp]'):
                     del case.attrib['timestamp']
+                for case in suite.findall('.//testcase[@file]'):
+                    del case.attrib['file']
+                for case in suite.findall('.//testcase[@line]'):
+                    del case.attrib['line']
                 self.root.append(suite)
             return