Remove smallestunit-disallowed-units.js.

It is covered by smallestunit-invalid-string.js and largestunit-smallestunit-mismatch.js.

test/built-ins/Temporal/PlainYearMonth/prototype/since/smallestunit-disallowed-units.js

@@ -1,28 +0,0 @@
-// Copyright (C) 2021 Igalia, S.L. All rights reserved.
-// This code is governed by the BSD license found in the LICENSE file.
-
-/*---
-esid: sec-temporal.plainyearmonth.prototype.since
-description: Since throws on disallowed or invalid smallestUnit
-features: [Temporal, arrow-function]
----*/
-
-const earlier = new Temporal.PlainYearMonth(2019, 1);
-const later = new Temporal.PlainYearMonth(2021, 9);
-
-[
-  'era',
-  'weeks',
-  'days',
-  'hours',
-  'minutes',
-  'seconds',
-  'milliseconds',
-  'microseconds',
-  'nanoseconds',
-  'nonsense'
-].forEach((smallestUnit) => {
-  assert.throws(RangeError, () => later.since(earlier, { smallestUnit }),`throws on disallowed or invalid smallestUnit: ${smallestUnit}`);
-});
-
-assert.throws(RangeError, () => later.since(earlier, { largestUnit: 'months', smallestUnit: 'years' }), 'throws if smallestUnit is larger than largestUnit');