[toolkit] Exclude printer spew from troubleshooting information.

In almost all cases this is pointless to include, a ton of useless entries,
and there's no reason to have people post a full enumeration of installed
printers on their system when asked for TS information.
If there's a printer specific issue, people can always be asked to post relevant
info manually.

toolkit/modules/Troubleshoot.jsm

@@ -96,6 +96,7 @@ const PREFS_WHITELIST = [
 const PREFS_BLACKLIST = [
   /^network[.]proxy[.]/,
   /[.]print_to_filename$/,
+  /^print[.]printer_/,
   /^print[.]macosx[.]pagesetup/,
 ];