Bug 1586814 - Add browser.contentblocking.category to about:support; r=johannh

Differential Revision: https://phabricator.services.mozilla.com/D48366

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

toolkit/modules/Troubleshoot.jsm

@@ -27,6 +27,7 @@ const PREFS_WHITELIST = [
   "accessibility.",
   "apz.",
   "browser.cache.",
+  "browser.contentblocking.category",
   "browser.display.",
   "browser.download.folderList",
   "browser.download.hide_plugins_without_extensions",