Fix changelog capturing of PRs from _AztecProtocol/aztec-packages_

[Savio-Sou]

Context

Barretenberg releases currently captures PRs into their changelogs assuming PR numbers all belong to this repo.

Problem

This works as expected with PRs created in this repo.

But when PRs are mirrored from AztecProtocol/aztec-packages, the release changelogs would be linking to https://github.com/AztecProtocol/barretenberg/<aztec-packages_PR_number>, which points to unrelated / non-existing PRs in this repo.

Example

Take v0.5.0 as an example:

Clicking "#1925" of "update to acvm 0.24.0" would link to AztecProtocol/barretenberg/issues/1925, rather than the actual PR AztecProtocol/aztec-packages/pull/1925.

Happy Case

Either the release-please or mirroring workflow should be fixed to cater for capturing mirrored PRs in changelogs appropriately.