cargo: Bump zlib-rs to 0.6.5

Fetching a large repository looped with

    Failed to consume the pack sent by the remote

even though the pack appears valid (Git indexes it in full).

The cause appears to be a bug in zlib-rs 0.6.3 according to
<https://github.com/trifectatechfoundation/zlib-rs/pull/504>.

Cargo.lock

@@ -5546,9 +5546,9 @@ dependencies = [
 
 [[package]]
 name = "zlib-rs"
-version = "0.6.3"
+version = "0.6.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3be3d40e40a133f9c916ee3f9f4fa2d9d63435b5fbe1bfc6d9dae0aa0ada1513"
+checksum = "5431d5661c32445236631278f27946e444ddafe4684cac70b185272d4f9c52d5"
 
 [[package]]
 name = "zmij"