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

firefox-esr: update to 115.12.0.
https://github.com/void-linux/void-packages/pull/50950

Description:
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#### Testing the changes
- I tested the changes in this PR: **YES**

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#### Local build testing
- I built this PR locally for my native architecture, x86_64-glibc
- I did not cross-build this PR locally as it costs nearly a hour to finish a single build.

Just a minor update, everything works as far as I can tell.