Update dependency wpackagist-plugin/activitypub to v5.4.1

This MR contains the following updates:

Package	Type	Update	Change
wpackagist-plugin/activitypub (source)	require	minor	5.2.0 -> 5.4.1

---

Configuration

Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

Automerge: Disabled by config. Please merge this manually once you are satisfied.

Rebasing: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox.

Ignore: Close this MR and you won't be reminded about this update again.

---

• If you want to rebase/retry this MR, check this box

---

This MR has been generated by Renovate Bot.

composer.json

@@ -114,7 +114,7 @@
         "wpackagist-plugin/event-organiser": "3.12.8",
         "noblogs/ai-authenticate-rest-api-plugin": "0.0.4",
         "wpackagist-plugin/multisite-custom-css": "1.0",
-        "wpackagist-plugin/activitypub": "5.3.0",
+        "wpackagist-plugin/activitypub": "5.3.1",
         "wpackagist-plugin/gallery-block-lightbox": "1.15",
         "wpackagist-plugin/unconfirmed": "1.3.7",
         "noblogs/wp-mat": "0.1.4",