tests: Dont add locales to test runtime on musl

musl libc doesn't provides locales under /usr/share/locales. The tests
still run fine without copying locale under musl.
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f