Fix flake8 `do not compare types` error

Please check if the PR fulfills these requirements
[X] Tests for the changes have been added
[x] Docs have been added / updated
[ ] All CI checks are green
What kind of change does this PR introduce? Build fix

What is the current behavior? Running tox -e py39 or pre-commit run --all-files leads to a flake8 failure:

detect_secrets/plugins/ibm_cloud_iam.py:37:8: E721 do not compare types, for exact checks use `is` / `is not`, for 
instance checks use `isinstance()`

What is the new behavior (if this is a feature change)? flake8 passes. For example:

(.venv)
abramowi at Marcs-MacBook-Pro-3 in ~/Code/OpenSource/detect-secrets (fix-flake8-do-not-compare-types-error●)
$ pre-commit run --all-files
Check builtin type constructor use.......................................Passed
Check docstring is first.................................................Passed
Debug Statements (Python)................................................Passed
Fix double quoted strings................................................Passed
Fix End of Files.........................................................Passed
Tests should end in _test.py.............................................Passed
Flake8...................................................................Passed
Trim Trailing Whitespace.................................................Passed
Reorder python imports...................................................Passed
Add trailing commas......................................................Passed
autopep8.................................................................Passed
Detect secrets...........................................................Passed

Does this PR introduce a breaking change? No
Other information:

Yelp / detect-secrets

Fix flake8 `do not compare types` error #716