fix(3p/rustsec-advisory-db): expose rev for nixpkgs-crate-holes

Not sure if this used to work or if I started using the rev attribute in
nixpkgs-crate-holes without actually testing it. The failure in any case
is hidden from CI as it occurs at runtime, being hidden behind a
function.

Change-Id: Ib1db5393554a699c7c4b18697a9c9c902e93a507
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5199
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>

third_party/rustsec-advisory-db/default.nix

@@ -21,4 +21,7 @@ pkgs.fetchFromGitHub {
     rev
     sha256
     ;
+  passthru = {
+    inherit (pin) rev;
+  };
 }