don't prevent unsigned addon warning to not break some addons
This broke installing some, but not all, addons. The reason is that some
addons derive their addon-id from a certificate's CommonName in
XPIInstall.jsm::loadManifest(aPackage, aLocation, aOldAddon)
bring the patch closer to the then-upstream comm-central. might have the
negative side-effect of being detectable by websites according to:
https://developer.mozilla.org/en-US/docs/Mozilla/Chrome_Registration
this hopefully makes the monkey patch update persistent.
Note: instead of using FileUtils, this would be another method:
const {Services} = Cu.import('resource://gre/modules/Services.jsm');
let manifest = Services.dirsvc.get('GreD', Ci.nsIFile);
manifest.append('legacy.manifest');