**Apache Airflow version**: 2.1.0

**What happened**:
Airflow logging assume dict_key is type `str`
```
    logging.info("Dictionary where key is int type: %s", modified_table_mapping)
  File "/usr/lib64/python3.6/logging/__init__.py", line 1902, in info
    root.info(msg, *args, **kwargs)
  File "/usr/lib64/python3.6/logging/__init__.py", line 1308, in info
    self._log(INFO, msg, args, **kwargs)
  File "/usr/lib64/python3.6/logging/__init__.py", line 1444, in _log
    self.handle(record)
  File "/usr/lib64/python3.6/logging/__init__.py", line 1453, in handle
    if (not self.disabled) and self.filter(record):
  File "/usr/lib64/python3.6/logging/__init__.py", line 720, in filter
    result = f.filter(record)
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 157, in filter
    record.__dict__[k] = self.redact(v)
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 193, in redact
    return {dict_key: self.redact(subval, dict_key) for dict_key, subval in item.items()}
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 193, in <dictcomp>
    return {dict_key: self.redact(subval, dict_key) for dict_key, subval in item.items()}
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 189, in redact
    if name and should_hide_value_for_key(name):
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 74, in should_hide_value_for_key
    name = name.strip().lower()
AttributeError: 'int' object has no attribute 'strip'
```

**How to reproduce it**:
Define a dictionary where the type of keys is `int` and print it in any Airflow tasks.

tests/utils/log/test_secrets_masker.py
'env',
                {'api_key': 'masked based on key name', 'other': 'foo'},
                {'api_key': '***', 'other': 'foo'},
            ),
        ],
    )
    def test_redact(self, patterns, name, value, expected):
        filt = SecretsMasker()
        for val in patterns:
            filt.add_mask(val)
        assert filt.redact(value, name) == expected
    def test_redact_filehandles(self, caplog):
        filt = SecretsMasker()
        with open("/dev/null", "w") as handle:
            assert filt.redact(handle, None) == handle
        
        assert caplog.messages == []
class TestShouldHideValueForKey:
    @pytest.mark.parametrize(
        ("key", "expected_result"),
        [
            ('', False),
            (None, False),
            ("key", False),
            ("google_api_key", True),
            ("GOOGLE_API_KEY", True),
            ("GOOGLE_APIKEY", True),
        ],
    )
    def test_hiding_defaults(self, key, expected_result):