Drop md5 and sha1 schemes from supported key schemes

[ckilcoin]

Fixes: #512

Drop md5 and sha1 schemes from supported key schemes without changing keys/ module.

Please verify and check that the pull request fulfils the following requirements:

• The code follows the Code Style Guidelines
• Tests have been added for the bug fix or new feature
• Docs have been added for the bug fix or new feature

Tested by running tox -e py311, no additional tests needed since it is a removal of schemes.

[jku]

Quick comment:

• In Drop md5 and sha1 schemes from supported key schemes #512 I suggested removing the support from signer module (so the signer/__init__.py key dispatch table)
• this PR also removes support from keys and hashes modules

This is probably still fine: nobody should be using these hash algorithms in the year 2023 (the theoretical danger is that existing keys used somewhere could stop working because of this... but I do think it's theoretical)

@lukpueh opinions?

[jku]

Also, please have a look at the lint results (you can check them locally too with tox -e lint)

[lukpueh]

This is probably still fine: nobody should be using these hash algorithms in the year 2023 (the theoretical danger is that existing keys used somewhere could stop working because of this... but I do think it's theoretical)

Agreed. IMO annoying potential users of md5, sha1 is a fair risk for us to take.

[jku]

LGTM