Using go install with latest version can cause CI unexpected breakages

[ishymko]

docs.yaml flow does go install with @latest which recently caused

go: github.com/bufbuild/buf/cmd/buf@latest: github.com/bufbuild/buf@v1.66.0 requires go >= 1.25.6 (running go 1.24.12; GOTOOLCHAIN=local)

without any changes to the source

(https://github.com/a2aproject/A2A/actions/runs/22359664144)

Such dependencies should probably be pinned in source control and managed by dependabot instead.