GitHub Actions: update action versions

[mgottscho]

No description provided.

[mgottscho]

This change is part of the following stack:

• Bazel: upgrade rules_python from 1.5.1 to 1.8.4 #19
  • Bazel: upgrade bazel_skylib from 1.8.1 to 1.9.0 #20
    • GitHub Actions: update action versions #21 ◀
      • Update Bazel minor version from 7.6.1 to 7.7.1 #22

_{Change managed by git-spice.}