Bug 1787570 - Bump cargo-vet to 0.3. r=nika

Differential Revision: https://phabricator.services.mozilla.com/D155758

taskcluster/ci/fetch/toolchains.yml

@@ -607,7 +607,7 @@ cargo-vet:
     fetch:
         type: git
         repo: https://github.com/mozilla/cargo-vet
-        revision: 2f4dbcb4dd77b54a0455c520647830267d908ddb
+        revision: 12e3593437263bd17b5c3d2626ea8346799bf4b1
 
 symbol-scrapers:
     description: Linux distribution symbol scraper source