Silence incorrect warning message

[AlanCoding]

Looks like this was introduced in #202

Fixes #288

This is annoying for me, because it can repeat the message 100s of times, depending on how much a project uses the pytest built-in request fixture. I don't know why that fixture does not have the expected properties like other fixtures, but it's not actually surprising because this is a core pytest object, and not a user fixture. The point of this is to warn on user fixtures, so I see no potential harm from this.

minor

[AlanCoding]

From CI failures:

debug - 2024-03-12 19:05:41,624 -- Commit creating result --- {"result": "RequestResult(error=RequestError(code='HTTP Error 429', params={}, description='{\"detail\":\"Tokenless has reached GitHub rate limit. Please upload using a token: https://docs.codecov.com/docs/adding-the-codecov-token. Expected available in 146 seconds.\"}'), warnings=[], status_code=429, text='{\"detail\":\"Tokenless has reached GitHub rate limit. Please upload using a token: https://docs.codecov.com/docs/adding-the-codecov-token. Expected available in 146 seconds.\"}')"}
error - 2024-03-12 19:05:41,625 -- Commit creating failed: {"detail":"Tokenless has reached GitHub rate limit. Please upload using a token: https://docs.codecov.com/docs/adding-the-codecov-token. Expected available in 146 seconds."}