GHA: Fix make_email-body script reference

This component was recently migrated from being inline, into a dedicated
script file.  This was necessary for testing.  However, it's hard to
test the actual github-actions workflow YAML, and there was a typo.  Fix
the reference to the script filename missing the `.sh` extension.

Ref: https://github.com/containers/podman/pull/16414

Signed-off-by: Chris Evich <cevich@redhat.com>

.github/workflows/check_cirrus_cron.yml

@@ -42,7 +42,7 @@ jobs:
 
             - if: steps.cron.outputs.failures > 0
               shell: bash
-              run: './.github/actions/check_cirrus_cron/make_email_body'
+              run: './.github/actions/check_cirrus_cron/make_email_body.sh'
 
             - if: steps.cron.outputs.failures > 0
               name: Send failure notification e-mail