Bug 1604785 - Exclude browser.fixup.domainwhitelist.* prefs from about:support r=adw

Differential Revision: https://phabricator.services.mozilla.com/D57629

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

toolkit/modules/Troubleshoot.jsm

@@ -102,6 +102,7 @@ const PREFS_WHITELIST = [
 
 // The blacklist, unlike the whitelist, is a list of regular expressions.
 const PREFS_BLACKLIST = [
+  /^browser[.]fixup[.]domainwhitelist[.]/,
   /^media[.]webrtc[.]debug[.]aec_log_dir/,
   /^media[.]webrtc[.]debug[.]log_file/,
   /^network[.]proxy[.]/,