Fix cancelled R CMD check workflow

[walkowif]

When merging/pushing to main, both check.yaml and docs.yaml workflows run.

Example: check.yaml and docs.yaml.

This causes the R CMD check job in check.yaml workflow to take precedence over the R CMD check job (for stable package versions) in docs.yaml workflow (which is responsible for checking the Catalog prior to rendering it for stable package versions). The R CMD check job in docs.yaml is then cancelled and the Catalog will not be rendered for stable package versions even if the R CMD check succeeded.

The proposed solution is to only run the R CMD check job in docs.yaml on push to main.

[github-actions[bot]]

Unit Tests Summary

    1 files  2 suites   58s :stopwatch:   26 tests 0 :heavy_check_mark:   26 :zzz: 0 :x: 286 runs  0 :heavy_check_mark: 286 :zzz: 0 :x:

Results for commit 34005c46.