Bug 1286428 - Stop reporting print.printer* preferences in about:support. r=Gijs

These are not generally used for support, and there can be many of them which makes the report larger and harder to understand.

Differential Revision: https://phabricator.services.mozilla.com/D18195

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

toolkit/modules/Troubleshoot.jsm

@@ -95,6 +95,7 @@ const PREFS_BLACKLIST = [
   /^network[.]proxy[.]/,
   /[.]print_to_filename$/,
   /^print[.]macosx[.]pagesetup/,
+  /^print[.]printer/,
 ];
 
 // Table of getters for various preference types.