New review comment by Logarithmus on void-packages repository

https://github.com/void-linux/void-packages/pull/30702#discussion_r627366464

Comment:
OK, I'll remove `rust-sccache` from the dependencies. Instead, I'll add a note into README.md that in order to use `sccache` with `xbps-src`, one should run `xbps-install -r masterdir/ rust-sccache`.