Fix Time#localtime(0) being treated as UTC.

Author: philr

core/src/main/java/org/jruby/RubyTime.java

@@ -632,8 +632,6 @@ public RubyTime localtime(ThreadContext context, IRubyObject arg) {
 
         if (zone == null) {
             throw invalidUTCOffset(context);
-        } else if (zone == DateTimeZone.UTC) {
-            return gmtime(context);
         }
 
         return adjustTimeZone(context, zone, true);