workflows/release-task: Use less privileged token for uploading release notes (#180299) (#180650)
We were using one token for both pushing to the llvmbot fork and for
creating a pull request against the www-releases repository, since the
fork and the repository have different owners, we were using a classic
access token which has very coarse-grained permissions. By using two
separate tokens, we limit the permissions to just what we need to do the
task.
This is a re-commit of b6ee085068972a41f3b2735a9f7e3ca48eab0f00 minus
the environment changes which were causing the workflow to fail.
(cherry picked from commit 48dffbc654f2a606025f4b14c9b789c99f8188ae)