Update tame-index/gix (#566)

This updates tame-index, which includes
EmbarkStudios/tame-index#33, which allows
cargo-deny to use OS file locking for safer interactions with cargo, as
well as improved safety and robustness for read/fetching advisory
databases.

This doesn't add new tests as I'm _pretty_ confident the OS file locking
code works correctly, which means #537 is basically covered since it's
more robust now.

Resolves: #537

.gitignore

@@ -4,3 +4,4 @@
 /tests/test_data/**/target
 scripts/check
 *.snap.new
+/tests/advisory-db/db.lock