test: verify $/ self-repo reference

Author: hujc7

.github/actions/request-docker-ci/action.yml

@@ -8,8 +8,7 @@ description: >
   Starts build.yaml ("Docker + Tests") by toggling the ``ci:run-docker`` label,
   which is the only event that workflow triggers on. The token must be a GitHub
   App installation token; GitHub does not cascade GITHUB_TOKEN actions into new
-  workflow runs, so a label applied with GITHUB_TOKEN starts nothing. Requires a
-  prior checkout.
+  workflow runs, so a label applied with GITHUB_TOKEN starts nothing.
 
 inputs:
   pr-number:

.github/workflows/nightly-isaacsim-image.yml

@@ -212,7 +212,7 @@ jobs:
 
       # Gated on branch_changed so an unchanged open PR does not re-spend GPU
       # minutes every night.
-      - uses: ./.github/actions/request-docker-ci
+      - uses: $/.github/actions/request-docker-ci
         if: ${{ steps.pin.outputs.branch_changed == 'true' && !inputs.dry_run }}
         with:
           pr-number: ${{ steps.pr.outputs.pr_number }}