chore(ci): always push release to azure (#2321)
PR #2048 changed the CI so that olean caches are not pushed to Azure if a later commit on the same branch occurs. The reasoning was that it was unlikely that anyone would fetch those caches. That's changed as of #2278, since `fetch_olean_cache.sh` now looks for caches from commits earlier in the history. This means that currently, we can observe the following wasteful sequence of events in several PRs (e.g. #2258):
1. commit A gets pushed to a certain branch and CI_A starts.
2. While CI_A is still running the `leanpkg build` step, commit B is pushed and CI_B starts.
3. CI_A finishes `leanpkg build` but doesn't upload its cache to Azure because of #2048
4. Now commit C is pushed and can't use the results of CI_A
5. CI_B finishes `leanpkg build` but doesn't upload its cache
6. Commit D is pushed and can't use the results of CI_A or CI_B ...
(This can keep happening as long as the next commit arrives before the most recent CI uploads to Azure).
I also cleaned up some stuff that was left over from when we ran the build on both "pr" and "push" events.
