ci: make github-bot ignore events emitted by codecov (gnolang#3274)

It's a bit of a "push and pray" since it would take too long to set up
to reproduce this on my test repo/org, but I've triple-checked the
documentation, the previous runs, etc., and it should be fine.

Related to
gnolang#3238 (comment)

<details><summary>Contributors' checklist...</summary>

- [ ] Added new tests, or not needed, or not feasible
- [ ] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [ ] Updated the official documentation or not needed
- [ ] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [ ] Added references to related issues and PRs
- [ ] Provided any useful hints for running manual tests
</details>

.github/workflows/bot.yml

@@ -33,8 +33,8 @@ jobs:
   # handle the parallel processing of the pull-requests
   define-prs-matrix:
     name: Define PRs matrix
-    # Prevent bot from retriggering itself
-    if: ${{ github.actor != vars.GH_BOT_LOGIN }}
+    # Prevent bot from retriggering itself and ignore event emitted by codecov
+    if: ${{ github.actor != vars.GH_BOT_LOGIN && github.actor != "codecov[bot]" }}
     runs-on: ubuntu-latest
     permissions:
       pull-requests: read