ci: Fix workflow events (#1446)

This was found by auditing workflows based on research published here:

https://github.com/joeyparrish/workflow-cheat-sheet

The research was prompted by a workflow bug in Shaka Streamer

.github/workflows/pr.yaml

@@ -26,7 +26,7 @@ on:
 # old one.  If a PR is updated and a new test run is started, the old test run
 # will be cancelled automatically to conserve resources.
 concurrency:
-  group: ${{ github.workflow }}-${{ inputs.ref || github.ref }}
+  group: ${{ github.workflow }}-${{ github.event.number || inputs.ref }}
   cancel-in-progress: true
 
 jobs:

.github/workflows/release-please.yaml

@@ -82,7 +82,7 @@ jobs:
     if: needs.release.outputs.release_created && needs.compute.outputs.latest
     uses: ./.github/workflows/publish-docs.yaml
     with:
-      ref: ${{ github.ref }}
+      ref: refs/tags/${{ needs.release.outputs.tag_name }}
 
   # Publish official docker image
   docker:
@@ -105,7 +105,7 @@ jobs:
     if: needs.release.outputs.release_created
     uses: ./.github/workflows/build.yaml
     with:
-      ref: ${{ github.ref }}
+      ref: refs/tags/${{ needs.release.outputs.tag_name }}
       self_hosted: ${{ needs.settings.outputs.self_hosted != '' }}
       debug: ${{ needs.settings.outputs.debug != '' }}