Editorial: options parameter is always present in DifferenceZonedDateTime

The `options` parameter is always present and always an object.

Author: anba

spec/zoneddatetime.html

@@ -1271,8 +1271,6 @@ <h1>
         </dd>
       </dl>
       <emu-alg>
-        1. If _options_ is not present, set _options_ to *undefined*.
-        1. Assert: Type(_options_) is Object or Undefined.
         1. If _ns1_ is _ns2_, then
           1. Return ! CreateDurationRecord(0, 0, 0, 0, 0, 0, 0, 0, 0, 0).
         1. Let _startInstant_ be ! CreateTemporalInstant(_ns1_).