chore: remove keyring mock

[sweatybridge]

What kind of change does this PR introduce?

tests

What is the new behavior?

• Remove custom keyring mock since upstream change has been merged.
• Go 1.24 toolchain broke our coverage reporting cmd/go: inconsistent coverage when using -coverprofile with packages without tests golang/go#70244 (comment).

Additional context

unblocks #3514

[coveralls]

Pull Request Test Coverage Report for Build 14829770213

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 51.351%

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Totals
Change from base Build 14829317180:	0.2%
Covered Lines:	6993
Relevant Lines:	13618

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💛 - Coveralls