Revert "Fix GitHub action; mod_perl does not (yet) work with Perl > 5.37"

Now that an updated release of mod_perl is available, we can go back to
testing against newer versions of Perl.

This reverts commit 88a64d8.

Author: bleargh45

.github/workflows/perl-ci.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
 
     container:
-      image: perldocker/perl-tester:5.36
+      image: perldocker/perl-tester:latest
 
     steps:
       - name: Setup GitHub user
@@ -99,6 +99,7 @@ jobs:
     strategy:
       matrix:
         perl-version:
+          - "latest"
           - "5.36"
           - "5.34"
           - "5.32"