Bug 1577726 - Ride along: Remove a directory which doesn't exist anymore r=andi

Differential Revision: https://phabricator.services.mozilla.com/D44145

--HG--
extra : moz-landing-system : lando

tools/rewriting/ThirdPartyPaths.txt

@@ -134,7 +134,6 @@ toolkit/components/jsoncpp/
 toolkit/components/normandy/vendor/
 toolkit/components/protobuf/
 toolkit/components/url-classifier/chromium/
-toolkit/components/url-classifier/protobuf/
 toolkit/components/utils/mozjexl.js
 toolkit/crashreporter/breakpad-client/
 toolkit/crashreporter/google-breakpad/