Use PPM_AUTOMATION secrets for helm dispatch

Align with the org-level secret pair provisioned by rstudio/github-iac
for the posit-package-manager-automation App. Replaces the generic
APP_ID / APP_PRIVATE_KEY names that predate the app-specific
migration.

Author: bschwedler

.github/workflows/production.yml

@@ -78,8 +78,8 @@ jobs:
         id: app-token
         uses: actions/create-github-app-token@v3
         with:
-          app-id: ${{ secrets.APP_ID }}
-          private-key: ${{ secrets.APP_PRIVATE_KEY }}
+          app-id: ${{ secrets.PPM_AUTOMATION_APP_ID }}
+          private-key: ${{ secrets.PPM_AUTOMATION_PEM }}
           owner: rstudio
           repositories: helm