[MNT]: `[ci doc]` doesn't skip Github tests.

### Summary

When putting `[ci doc]` in the commit message, the GitHub tests all still run.  

https://github.com/matplotlib/matplotlib/blob/389a7e8889c25d05afab4e9ba7ce43e56cf82a99/.github/workflows/tests.yml#L39 is supposed to cause a skip, but I suspect https://github.com/matplotlib/matplotlib/pull/25145 broke this?

ping @ksunden

### Proposed fix

_No response_