Polyfill: Fix IsOffsetTimeZoneIdentifier to not accept sub-minute off…

…sets

This did not actually lead to any buggy behaviour, as far as I could tell.
But it should match the spec text, which parses
UTCOffset[~SubMinutePrecision] here.

polyfill/lib/ecmascript.mjs

@@ -2143,7 +2143,7 @@ export function TemporalZonedDateTimeToString(
 }
 
 export function IsOffsetTimeZoneIdentifier(string) {
-  return Call(RegExpPrototypeTest, OFFSET, [string]);
+  return Call(RegExpPrototypeTest, OFFSET_IDENTIFIER, [string]);
 }
 
 export function ParseDateTimeUTCOffset(string) {