Bug 1727264 - Make nsIRelativeFilePref scriptable again. r=KrisWright DONTBUILD

Thunderbird needs this to use nsIRelativeFilePref in JS.

Differential Revision: https://phabricator.services.mozilla.com/D123423

modules/libpref/nsIRelativeFilePref.idl

@@ -17,7 +17,7 @@ interface nsIFile;
  *
  */
 
-[uuid(2f977d4e-5485-11d4-87e2-0010a4e75ef2)]
+[scriptable, uuid(2f977d4e-5485-11d4-87e2-0010a4e75ef2)]
 interface nsIRelativeFilePref : nsISupports
 {
   /**