Reenable removed tests in test_registrar (#15790)

Improvements for detecting file removal have been introduced a while
ago. Filebeat doesn't wait until EOF when trying to detect removal. On
windows we also introduced some extra API call to detect file-deletion
flags being set.

filebeat/tests/system/test_registrar.py

@@ -820,7 +820,6 @@ def test_clean_inactive(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(file3)
 
-    @unittest.skipIf(os.name == 'nt', 'flaky test https://github.com/elastic/beats/issues/7690')
     def test_clean_removed(self):
         """
         Checks that files which were removed, the state is removed
@@ -870,7 +869,6 @@ 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')
     def test_clean_removed_with_clean_inactive(self):
         """
         Checks that files which were removed, the state is removed