RFR: Fix jextract GHA

[Jorn Vernee]

On Fri, 29 Apr 2022 11:14:39 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> the action does not ignore pr/* branches, which seems to be the norm in JDK

I left that one out since the jextract repo doesn't seem to have `pr/*` branches (as opposed to the jdk repo), so it didn't seem needed. But, it doesn't hurt to have that exclusion rule either I think.

-------------

PR: https://git.openjdk.java.net/jextract/pull/28