crates.io: remove badges
crates.io: remove badges

... and don't replace them with anything because crates.io does not
support GitHub Actions yet. But it's almost there:
https://github.com/rust-lang/crates.io/pull/1838

Thanks @atouchet for noticing this.

BurntSushi/ripgrep,BurntSushi/ripgrep,BurntSushi/ripgrep,BurntSushi/ripgrep