Editorial: CombineDateAndTimeDuration in NudgeToZonedTime is infallible

dateDuration and roundedTimeDuration cannot have opposite signs, so the
operation can't throw.

dateDuration must have the same sign as duration, because dayDelta either
is 0 or also has the same sign as duration.

roundedTimeDuration must have the same sign as duration or be 0, because
either it is rounded from duration in step 10, or it is rounded from
beyondDaySpan in step 12.c. beyondDaySpan also cannot have the opposite
sign as duration if we go into the substeps of step 12.

See: #3023

Author: ptomato

spec/duration.html

@@ -1695,7 +1695,7 @@ <h1>
           1. Let _dayDelta_ be 0.
           1. Let _nudgedEpochNs_ be AddTimeDurationToEpochNanoseconds(_roundedTimeDuration_, _startEpochNs_).
         1. Let _dateDuration_ be ! AdjustDateDurationRecord(_duration_.[[Date]], _duration_.[[Date]].[[Days]] + _dayDelta_).
-        1. Let _resultDuration_ be ? CombineDateAndTimeDuration(_dateDuration_, _roundedTimeDuration_).
+        1. Let _resultDuration_ be ! CombineDateAndTimeDuration(_dateDuration_, _roundedTimeDuration_).
         1. Return Duration Nudge Result Record { [[Duration]]: _resultDuration_, [[NudgedEpochNs]]: _nudgedEpochNs_, [[DidExpandCalendarUnit]]: _didRoundBeyondDay_ }.
       </emu-alg>
     </emu-clause>