CP-29639: Bump golang from 1.26.5-alpine to 1.27.0-alpine in /docker

[dependabot]

Bumps golang from 1.26.5-alpine to 1.27.0-alpine.

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

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[greptile-apps]

PR author is in the excluded authors list.

[amfelso]

Superseded by #983, which bumps Go to 1.26.7 across all seven references (three Dockerfiles + four go.mod directives).

This PR couldn't pass custom-checks on its own: scripts/ci-checks.sh requires the Go version to agree between every Dockerfile and every go.mod, and Dependabot can only edit docker/Dockerfile. #983 makes the coordinated change.

#983 targets 1.26.7 rather than 1.27.0 to keep it a patch-level bump — the six stdlib CVEs currently failing the Grype scan are all fixed in 1.26.6. A 1.27.0 move is a language minor-version change and is worth its own PR if we want it.

[dependabot]

OK, I won't notify you again about this release, but will get in touch when a new version is available. If you'd rather skip all updates until the next major or minor version, let me know by commenting @dependabot ignore this major version or @dependabot ignore this minor version. You can also ignore all major, minor, or patch releases for a dependency by adding an ignore condition with the desired update_types to your config file.

If you change your mind, just re-open this PR and I'll resolve any conflicts on it.