LibJS: Mark two calls as infallible in DifferenceTemporalPlainTime

This is an editorial change in the Temporal spec.

See: https://github.com/tc39/proposal-temporal/commit/0e4966a

Userland/Libraries/LibJS/Runtime/Temporal/PlainTime.cpp

@@ -619,10 +619,10 @@ ThrowCompletionOr<Duration*> difference_temporal_plain_time(GlobalObject& global
     // 12. Let result be ! DifferenceTime(temporalTime.[[ISOHour]], temporalTime.[[ISOMinute]], temporalTime.[[ISOSecond]], temporalTime.[[ISOMillisecond]], temporalTime.[[ISOMicrosecond]], temporalTime.[[ISONanosecond]], other.[[ISOHour]], other.[[ISOMinute]], other.[[ISOSecond]], other.[[ISOMillisecond]], other.[[ISOMicrosecond]], other.[[ISONanosecond]]).
     auto result = difference_time(temporal_time.iso_hour(), temporal_time.iso_minute(), temporal_time.iso_second(), temporal_time.iso_millisecond(), temporal_time.iso_microsecond(), temporal_time.iso_nanosecond(), other->iso_hour(), other->iso_minute(), other->iso_second(), other->iso_millisecond(), other->iso_microsecond(), other->iso_nanosecond());
 
-    // 13. Set result to (? RoundDuration(0, 0, 0, 0, result.[[Hours]], result.[[Minutes]], result.[[Seconds]], result.[[Milliseconds]], result.[[Microseconds]], result.[[Nanoseconds]], roundingIncrement, smallestUnit, roundingMode)).[[DurationRecord]].
-    auto rounded_result = TRY(round_duration(global_object, 0, 0, 0, 0, result.hours, result.minutes, result.seconds, result.milliseconds, result.microseconds, result.nanoseconds, rounding_increment, *smallest_unit, rounding_mode)).duration_record;
+    // 13. Set result to (! RoundDuration(0, 0, 0, 0, result.[[Hours]], result.[[Minutes]], result.[[Seconds]], result.[[Milliseconds]], result.[[Microseconds]], result.[[Nanoseconds]], roundingIncrement, smallestUnit, roundingMode)).[[DurationRecord]].
+    auto rounded_result = MUST(round_duration(global_object, 0, 0, 0, 0, result.hours, result.minutes, result.seconds, result.milliseconds, result.microseconds, result.nanoseconds, rounding_increment, *smallest_unit, rounding_mode)).duration_record;
 
-    // 14. Set result to ? BalanceDuration(0, result.[[Hours]], result.[[Minutes]], result.[[Seconds]], result.[[Milliseconds]], result.[[Microseconds]], result.[[Nanoseconds]], largestUnit).
+    // 14. Set result to ! BalanceDuration(0, result.[[Hours]], result.[[Minutes]], result.[[Seconds]], result.[[Milliseconds]], result.[[Microseconds]], result.[[Nanoseconds]], largestUnit).
     result = MUST(balance_duration(global_object, 0, rounded_result.hours, rounded_result.minutes, rounded_result.seconds, rounded_result.milliseconds, rounded_result.microseconds, Crypto::SignedBigInteger { (i32)rounded_result.nanoseconds }, *largest_unit));
 
     // 15. Return ! CreateTemporalDuration(0, 0, 0, 0, sign × result.[[Hours]], sign × result.[[Minutes]], sign × result.[[Seconds]], sign × result.[[Milliseconds]], sign × result.[[Microseconds]], sign × result.[[Nanoseconds]]).