fix(auth): more linting rules

[o-santi]

What kind of change does this PR introduce?

Add more ruff linting rules to auth, to catch unused variables, unused imports, and untyped return functions, inspired by #1288, which was caused by a missing return type.

Additional context

This should be done to the other packages as well, but auth has the highest priority since it is the biggest one by functionality, so it is the most probable to have these kinds of issues.

[coveralls]

Pull Request Test Coverage Report for Build 18980553623

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 214 unchanged lines in 12 files lost coverage.
• Overall coverage increased (+0.008%) to 92.567%

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Files with Coverage Reduction	New Missed Lines	%
tests/test_helpers.py	2	98.92%
src/supabase_auth/helpers.py	2	95.39%
tests/_sync/test_gotrue.py	3	99.02%
tests/_sync/test_gotrue_admin_api.py	3	98.96%
tests/_async/test_gotrue.py	3	99.02%
tests/_async/clients.py	4	91.03%
tests/_sync/clients.py	4	92.31%
tests/_async/test_gotrue_admin_api.py	5	98.27%
src/supabase_auth/_sync/gotrue_admin_api.py	9	80.0%
src/supabase_auth/_async/gotrue_admin_api.py	9	80.0%

Totals
Change from base Build 18973221892:	0.008%
Covered Lines:	8755
Relevant Lines:	9458

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💛 - Coveralls