Pin dependency wpackagist-plugin/activitypub to 0.13.4

This MR contains the following updates:

Package	Type	Update	Change
wpackagist-plugin/activitypub (source)	require	pin	^0.13.4 -> 0.13.4

Add the preset :preserveSemverRanges to your config if you don't want to pin your dependencies.

---

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 is behind base branch, 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, click this checkbox.

---

This MR has been generated by Renovate Bot.