Set secure and samesite when deleting remember cookie

[mo-lukecarr]

This PR introduces a fix for the issue reported in #683. As per the linked issue, in some browsers, the expectation is to set the same values for Secure and SameSite when deleting as were set when creating the cookie.

The implementation in this PR changes the call to response.delete_cookie to set the same secure and samesite argument values as were set when response.set_cookie is invoked. In the implementation, I've also added code comments to have the structure of the _clear_cookie method mirror that of the _set_cookie method (where secure and samesite are initially set on cookies).

All checks are passing locally using tox:

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As an aside, this is my first time contributing on this repository, and I noticed a dead link in the CONTRIBUTING.md file, so I've corrected it in this PR. Apologies if this makes the PR less granular and isn't strictly adhering to PR etiquette!

[coveralls]

coverage: 95.968% (+0.02%) from 95.951%
when pulling 548f8b9 on mo-lukecarr:clear-cookie-fix
into 26d12ea on maxcountryman:main.

[coveralls]

coverage: 95.968% (+0.02%) from 95.951%
when pulling 548f8b9 on mo-lukecarr:clear-cookie-fix
into 26d12ea on maxcountryman:main.