gitea-runner: update checksum for 1.0.8 release

[stefanb]

Ref:

• go 1.27rc2, go@1.26 1.26.5 (new formula) #288803
• gitea-mcp-server: update checksum for 1.3.0 release #288966

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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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• AI was used to generate or assist with generating this PR. Please specify below how you used AI to help you, and what steps you have taken to manually verify the changes.

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[stefanb]

Gitea seems to change checksum on every request:

$ curl -sL https://gitea.com/gitea/runner/archive/v1.0.8.tar.gz | shasum -a 256
3f634b66b2de25b2d7cb722981f29f0c64db657cb944b804eed6149c7f1e598f  -
$ curl -sL https://gitea.com/gitea/runner/archive/v1.0.8.tar.gz | shasum -a 256
ae4f06411eb5eac76d3a4e5b02abb7ec6cd0a3dbb37420e9cd3abf45d0d3f125  -
$ curl -sL https://gitea.com/gitea/runner/archive/v1.0.8.tar.gz | shasum -a 256
1df12630ed235fbf68ebd32704850461c01941803644647352c0f3ff75f3370c  -

[stefanb]

Superseded by

• gitea-runner: use git instead of archive #290372