build: niv advisory-db: update c5ebb272 -> 7c81bd4f (#1410)

## Changelog for advisory-db:
Branch: master
Commits: [rustsec/advisory-db@c5ebb272...7c81bd4f](rustsec/advisory-db@c5ebb27...7c81bd4)

* [`8b068177`](rustsec/advisory-db@8b06817) Add use-after-free advisory for `yottadb 1.1.0` and earlier
* [`be43bc8c`](rustsec/advisory-db@be43bc8) Assigned RUSTSEC-2021-0022 to yottadb
* [`221ec336`](rustsec/advisory-db@221ec33) rand_core: incorrect check on buffer length when seeding RNGs ([RustSec/advisory-db⁠#764](http://r.duckduckgo.com/l/?uddg=https://github.com/RustSec/advisory-db/issues/764))
* [`7c81bd4f`](rustsec/advisory-db@7c81bd4) Assigned RUSTSEC-2021-0023 to rand_core ([RustSec/advisory-db⁠#771](http://r.duckduckgo.com/l/?uddg=https://github.com/RustSec/advisory-db/issues/771))

nix/sources.json

@@ -6,10 +6,10 @@
         "homepage": "https://rustsec.org",
         "owner": "RustSec",
         "repo": "advisory-db",
-        "rev": "c5ebb27269da647a6d38a4b84a33d14e4da72ec0",
-        "sha256": "0p3rqbmcp8g8rxx4hn9pnhg9j780pva26li3qkn1zak03mdjwrb9",
+        "rev": "7c81bd4fc3cccbfe03f3ae977d691dcea620297b",
+        "sha256": "1qhdbj5mmilj5lxjhxyy6i44sqw955f8i139hkvfrl5507kdnm25",
         "type": "tarball",
-        "url": "https://github.com/RustSec/advisory-db/archive/c5ebb27269da647a6d38a4b84a33d14e4da72ec0.tar.gz",
+        "url": "https://github.com/RustSec/advisory-db/archive/7c81bd4fc3cccbfe03f3ae977d691dcea620297b.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "agent-js-monorepo": {