Right now we're attempting to remove tags associated with diffs that have been "Closed" or "Abandoned".
However, we didn't have a check to see whether or not the tag actually existed on remote (eg had already been removed). This was fine since the command to remove git tag is idempotent and we just get a warning (see below) when we attempt to delete a tag that doesn't exist.
```
remote: warning: deleting a non-existent ref
```
However, after pushing to `master` and kicking off the first run of the workflow, these extra commands can be pretty slow (https://github.com/CommE2E/comm/runs/7618422763?check_suite_focus=true).
Just added a `.filter(...)` to `getGitTagsToBeRemoved` to ensure that we only run the git remove tag command for tags that actually exist at remote. I totally should have done this earlier tbh.