chore (SPLAT-352): pin github actions to commit hash

[karol-karpinski]

This pull request updates the GitHub Actions workflow to use a specific commit hash for the pkg-size/action dependency instead of a version tag, ensuring more consistent and reproducible builds.

[github-actions]

📊 Package size report   No changes

File	Before	After
Total (Includes all files)	11.9 kB	11.9 kB
Tarball size	4.6 kB	4.6 kB

Unchanged files

File	Size
package.json	5.6 kB
README.md	6.3 kB

_{🤖 This report was automatically generated by pkg-size-action}