feat(rustsec-advisory-db): update to 2021-10-08 via nix-prefetch-git

This makes it much easier to update the db manually and also lays the
foundation for future automation bumping the advisory db.

Change-Id: I1244020c8bb1af43bf4e207c55f6420eb3f57bcf
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3713
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: Profpatsch <mail@profpatsch.de>

third_party/rustsec-advisory-db/pin.json

@@ -0,0 +1,11 @@
+{
+  "url": "https://github.com/RustSec/advisory-db.git",
+  "rev": "d29205a680bb8b3a22eaba6e9b2a5a6580274af0",
+  "date": "2021-10-08T18:17:22+02:00",
+  "path": "/nix/store/nm8nwgdyrs6mi9dydf6vylc833i3alnn-advisory-db",
+  "sha256": "0h08kfn2878k5l0qdsxikakrjbqbn6fb8f95zxpqfh5hqzn7mb6b",
+  "fetchLFS": false,
+  "fetchSubmodules": false,
+  "deepClone": false,
+  "leaveDotGit": false
+}