(CI) Run acceptance tests against puppetcore8-nightly

Pass the --nightly flag to the module_acceptance reusable workflow so
acceptance tests run against the puppetcore8-nightly collection, matching
other modules such as puppetlabs-apache. Without it, acceptance runs
against the released puppetcore8 collection.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: SugatD

.github/workflows/ci.yml

@@ -16,4 +16,6 @@ jobs:
   Acceptance:
     needs: Spec
     uses: "puppetlabs/cat-github-actions/.github/workflows/module_acceptance.yml@main"
+    with:
+      flags: "--nightly"
     secrets: "inherit"

.github/workflows/nightly.yml

@@ -15,4 +15,6 @@ jobs:
   Acceptance:
     needs: Spec
     uses: "puppetlabs/cat-github-actions/.github/workflows/module_acceptance.yml@main"
+    with:
+      flags: "--nightly"
     secrets: "inherit"