remove unused variable

It never made sense here to save self.init() which returns a string
containing a log or stdout or something, and which was never actually
used.

Also we then overwrote the variable with a pathname...

unittests/allplatformstests.py

@@ -2618,7 +2618,7 @@ class AllPlatformTests(BasePlatformTests):
 
     def test_introspect_json_flat(self):
         testdir = os.path.join(self.unit_test_dir, '57 introspection')
-        out = self.init(testdir, extra_args=['-Dlayout=flat'])
+        self.init(testdir, extra_args=['-Dlayout=flat'])
         infodir = os.path.join(self.builddir, 'meson-info')
         self.assertPathExists(infodir)