ci: update pkgdown action to reuse CCBR/actions

Author: kelly-sovacool

.github/actions/install-r-pak/action.yml

@@ -33,7 +33,7 @@ jobs:
           use-public-rspm: true
           r-version: 4.3
 
-      - uses: ./.github/actions/install-r-pak
+      - uses: CCBR/actions/install-r-pak@main
         with:
           versions-file: .github/package-versions.txt
           extra-packages: local::.