feat(CI): add sentence about use of AI in new contributors comment (leanprover-community#36141)

Author: robin-carlier

.github/workflows/label_new_contributor.yml

@@ -104,7 +104,7 @@ jobs:
           header: 'New Contributor Welcome'
           message: |
             ## Welcome new contributor!
-            Thank you for contributing to Mathlib! If you haven't done so already, please review our [contribution guidelines](https://leanprover-community.github.io/contribute/index.html), as well as the [style guide](https://leanprover-community.github.io/contribute/style.html) and [naming conventions](https://leanprover-community.github.io/contribute/naming.html).
+            Thank you for contributing to Mathlib! If you haven't done so already, please review our [contribution guidelines](https://leanprover-community.github.io/contribute/index.html), as well as the [style guide](https://leanprover-community.github.io/contribute/style.html) and [naming conventions](https://leanprover-community.github.io/contribute/naming.html). In particular, we kindly remind contributors that we have [guidelines](https://leanprover-community.github.io/contribute/index.html#use-of-ai) regarding the use of AI when making pull requests.
 
             We use a [review queue](https://leanprover-community.github.io/queueboard/review_dashboard.html) to manage reviews. If your PR does not appear there, it is probably because it is not successfully building (i.e., it doesn't have a green checkmark), has the `awaiting-author` tag, or another reason described in the [Lifecycle of a PR](https://leanprover-community.github.io/contribute/index.html#lifecycle-of-a-pr). The review dashboard has [a dedicated webpage](https://leanprover-community.github.io/queueboard/on_the_queue.html?search=${{ github.event.pull_request.number }}) which shows whether your PR is on the review queue, and (if not), why.