Update Node version to address deprecation warning. (#148)

GitHub have deprecated NodeJS v20 as an environment for actions,
and will be using NodeJS v24 for all actions from 2nd June 2026[1].

Currently GitHub runners print a deprecation warning in their logs
showing all actions that use the node20 environment, which includes
setup-bazel, so I'm updating the action to use node24, and so remove
it from the deprecation warning.

[1] https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Author: alsutton

action.yml

@@ -51,7 +51,7 @@ inputs:
     default: ${{ github.token }}
 
 runs:
-  using: node20
+  using: node24
   main: dist/main/index.js
   post: dist/post/index.js
   post-if: "!cancelled()"