ci(deploy): stop installing gettext for a caller that no longer exists

509cd19985 added gettext-base because the Act runner image lacks what
GitHub's ubuntu-latest ships, and coredns.py shelled out to envsubst. That
only ever covered the outer runner: the nested deploy containers it also
failed in are not reachable from an apt call in the job.

00478b8ead removed the dependency instead, substituting the Corefile through
string.Template in-process. git grep envsubst at HEAD now finds four hits and
none of them is a call: this step's name, the docstring that explains the
change, and two stale README lines.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.github/workflows/call-test-deploy.yml

@@ -149,9 +149,9 @@ jobs:
           set -euo pipefail
           echo "GITHUB_REPOSITORY_OWNER=$(scripts/meta/resolve/repository/owner.sh)" >> "$GITHUB_ENV"
 
-      - name: 📦 Install deps (jq + envsubst)
+      - name: 📦 Install jq
         shell: bash
-        run: ./scripts/install/apt.sh jq gettext-base
+        run: ./scripts/install/apt.sh jq
 
       - name: 🔧 Set up Python
         uses: actions/setup-python@v6