Allow bump MDC deps action to trigger tests (#720)

I signed into the tedium-bot (Polymer automation account) GitHub page, created a Personal access token, and added it to this repo's secrets as TEDIUM_BOT_GITHUB_ACCESS_TOKEN.

By using this token instead of the automatically populated GITHUB_TOKEN token, subsequent GitHub Actions will be allowed to run on the PR we create (i.e. tests).

.github/workflows/bump-mdc-deps.yml

@@ -33,7 +33,7 @@ jobs:
       # https://github.com/github/hub instead?
       uses: peter-evans/[email protected]
       env:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        GITHUB_TOKEN: ${{ secrets.TEDIUM_BOT_GITHUB_ACCESS_TOKEN }}
         COMMIT_MESSAGE: Auto bump MDC Web deps to ${{ steps.bump.outputs.new-mdc-version }}
         # TODO Find or make an account that is whitelisted to not trigger the# CLA check.
         COMMIT_AUTHOR_EMAIL: [email protected]