Cherry-pick #18134 to 7.x: Skip flaky clean_x tests in filebeat (#18190)

filebeat/tests/system/test_registrar.py

@@ -869,7 +869,7 @@ def test_clean_removed(self):
         # Make sure the last file in the registry is the correct one and has the correct offset
         assert data[0]["offset"] == self.input_logs.size(file2)
 
-    @unittest.skip('flaky test https://github.com/elastic/beats/issues/10606')
+    @unittest.skipIf(os.name == 'nt', 'flaky test https://github.com/elastic/beats/issues/10606')
     def test_clean_removed_with_clean_inactive(self):
         """
         Checks that files which were removed, the state is removed