use PULUMI_BOT_TOKEN for release (#79)

The BOT_GITHUB_TOKEN seems to be a classic PAT, which we no longer
allow to access repos in the pulumi org.  Switch this to the
PULUMI_BOT_TOKEN, which I *think* is a valid fine-grained PAT.

.github/workflows/release.yml

@@ -21,7 +21,7 @@ jobs:
           version: latest
           args: release --rm-dist
         env:
-          GITHUB_TOKEN: ${{ secrets.BOT_GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.PULUMI_BOT_TOKEN }}
       - name: Chocolatey Package Deployment
         run: |
           make install