There's a merged pull request on the void-packages repository

Firefox ESR: update to 91.9.0
https://github.com/void-linux/void-packages/pull/36212

Description:
Testing the changes:

`I tested the changes in this PR: extensively (x86_64-glibc)`

Local build testing:

`I built this PR for x86_64-glibc, x86_64-musl and aarch64`

[ci skip]