ci: Run PR Reporter even against PRs from forks

[rschristian]

For a while now we haven't been getting benchmark comments on PRs from forks (e.g., #4642), only realized once @jviide brought it up last week.

It's a big time range, but as of #4325 it was working, and by #4471 it was not, and we didn't have any alterations to our config during that time.

Did some debugging in another repo and, as best as I can tell, it seems like it's the branches config that is the issue and seems to be born from a change GitHub made (due to use not altering this field, or any other, during the time frame mentioned above). If we remove that filter the reporter does seem to run just fine, with it, it never gets picked up. This config should be unnecessary anyhow, as the default behavior is to track everything, so removal seems correct.

[coveralls]

coverage: 99.618%. remained the same
when pulling 2094be8 on ci/fix-pr-reporter-forks
into 4b7e231 on main.