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

Firefox ESR: update to 91.7.0
https://github.com/void-linux/void-packages/pull/36084

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

[skip CI]