Bug 1898890 - Port bug 1898558 - Switch the license linter to use an exclusion list for tests that is defined in the yaml rather than in the linter itself. r=aleca

With this, `./mach commlint -l license` works like its m-c counterpart.

Differential Revision: https://phabricator.services.mozilla.com/D211723

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

tools/lint/license.yml

@@ -25,6 +25,7 @@ license:
         - comm/mailnews/jsaccount/readme.html
         # License file in directory
         - comm/mailnews/mime/jsmime
+        - '**/test*'
     extensions:
         - .c
         - .cc