PlainTime should not implement toZonedDateTime

[rkh]

This polyfill adds a non-spec PlainTime.prototype.toZonedDateTime.

This function is incompatible with the signature of any other toZonedDateTime function, meaning that this code breaks with the polyfill:

// value being any temporal object
if ('toZonedDateTime' in value) value.toZonedDateTime('UTC').epochMilliseconds;

[fabon-f]

PlainTime.prototype.toZonedDateTime was in the spec but removed last year (tc39/proposal-temporal#2895), and the polyfill has not been yet updated since then.
Of course the update is planned, see #47 for the detail.

[rkh]

Thanks, was searching to toZonedDateTime specifically and thus missed the ticket. Will close this one in favor of #47.