percona-toolkit: update checksum for 3.7.1 release

[stefanb]

Ref (chronological):

• https://docs.percona.com/percona-toolkit/release_notes.html#v3-7-1-released-2025-12-17
• https://github.com/percona/percona-toolkit/releases/tag/v3.7.1
• percona-toolkit 3.7.1 #259356
• percona-toolkit: install missing go tools #263460 (PT-2506 make install does not install go tools percona/percona-toolkit#1052)
• https://docs.percona.com/percona-toolkit/release_notes.html#v3-7-1-3-released-2026-04-17
• go 1.27rc1, go@1.26 1.26.4 (new formula) #288803

https://github.com/percona/percona-toolkit/blob/3.x/Changelog

Side quest: No separate tag / release 3.7.1-3?

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• Have you followed the guidelines for contributing?
• Have you ensured that your commits follow the commit style guide?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>?
• Is your test running fine brew test <formula>?
• Does your build pass brew audit --strict <formula> (after doing HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

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