bug#46925: Ripgrep tests failures due to bstr update

[John Soo]

Hi Guix,

I just talked to burntsushi on github about the failing ripgrep tests.
It looks like the version of bstr we are now using changed the
representation of bstrs and caused us test failures.  Changing the
version of bstr used in ripgrep@12.1.1 to 0.2.12 should fix the problem.

See https://github.com/BurntSushi/ripgrep/discussions/1813

Thanks!

John