Minor tweaks to issue-opening bot

[larsoner]

Leaving as draft for a few days in case there are other tweaks now that we have issues in the open. But from looking and using it:

1. Add job-level annotations (I was on a job page and saw nothing -- redundant with the action summary but puts in two places which helps discoverability)
2. Add 🤖 to last line of opened issue to make it visually clearer it's a bot-opened issue
3. Tweak dry-run wording (it says it opened the issue... but it would open the issue)
4. Adds note that the "last updated" on the Anaconda site is not the last uploaded wheel -- deleting an old wheel counts as an update (and so the "last updated" date reflects the deletion date, not the most-recent-upload date)