github actions: Use 7.9.2009 vault package path

I'm honestly not sure why this is necessary now, but this ensures
that rinse is able to download and install the centos 7 rpms in
the build chroot

Author: bmastbergen

.github/workflows/build-check_x86_64.yml

@@ -24,7 +24,7 @@ jobs:
       - name: Build centos7 chroot
         run: |
           sudo rinse --distribution centos-7 \
-                --mirror http://dl.rockylinux.org/vault/centos/7/os/x86_64/Packages \
+                --mirror http://dl.rockylinux.org/vault/centos/7.9.2009/os/x86_64/Packages \
                 --arch amd64 \
                 --directory centos-7-chroot