lang/rust: Udpate checksums in libgit2-sys/.cargo-checksum.json

It was part of the initial patch from Charlie Li to support LibreSSL
2.7. However, I misread it and though he was only removing bits
which were not needed anymore (updating checksums for openssl and
openssl-sys).

Now, we update all three: libgit2-sys, openssl and openssl-sys.

PR: 226955
Submitted by: Charlie Li <ml+freebsd@vishwin.info>
Reported by: Charlie Li <ml+freebsd@vishwin.info>