[chore] updates go-mutexes to no longer rely on unsafe linkname

[NyaaaWhatsUpDoc]

Description

Again, this is to prepare us for the Go 1.23 release. No more unsafe linkname in the mutex map, in fact most of the use wasn't really needed given sync.Cond{} is a thin wrapper around a runtime gated type. The only unsafe usage now in it is: https://codeberg.org/gruf/go-mutexes/src/commit/1a593cc53db2a09ec1c52e18797eaa625ea4292d/map.go#L188

The actual diff can be seen here: https://codeberg.org/gruf/go-mutexes/compare/v1.5.0...v1.5.1

Checklist

• I/we have read the GoToSocial contribution guidelines.
• I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
• I/we have not leveraged AI to create the proposed changes.
• I/we have performed a self-review of added code.
• I/we have written code that is legible and maintainable by others.
• I/we have commented the added code, particularly in hard-to-understand areas.
• I/we have made any necessary changes to documentation.
• I/we have added tests that cover new code.
• I/we have run tests and they pass locally with the changes.
• I/we have run go fmt ./... and golangci-lint run.