JP22: 23.2.3.2 Set.prototype.clear should have NOTES like Map.prototype.clear

[Constellation]

Map.prototype.clear has NOTES, but Set.prototype.clear does not.
Since Map.prototype.delete and Set.prototype.delete has the almost same notes, to keep consistency, I think adding NOTES to Set.prototype.clear is preferable.

like,

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NOTE The existing [[SetData]] List is preserved because there may be existing SetIterator objects that are suspended midway through iterating over that List.

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http://ecma-international.org/ecma-262/6.0/#sec-set.prototype.clear