fix(spec): correct the offer-set claim in the icon-withdrawal CHANGELOG entry

Part of #14407 — packages/spec/CHANGELOG.md:6702 said the options repeater
offers "exactly SelectOptionSchema's authorable keys minus visibleWhen".
SelectOptionSchema declares six authorable keys (label, value, description,
color, default, visibleWhen); the repeater offers four
(label/value/color/description, pinned by field-rows-option-description.test.ts).
The unoffered set is { default, visibleWhen }, not { visibleWhen } alone.

Text-only correction. No packages/spec/src/** file touched, no accept/reject
behaviour moves, no public surface widens.

The correction lands in CHANGELOG.md rather than the withdrawn .changeset/
entry because a Version Packages release already folded that changeset
(@objectstack/spec is now 17.3.0) between triage's ruling and this pickup.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01G4138K1EG7kQ81FNba5Kp4

Author: claude

packages/spec/CHANGELOG.md

@@ -6699,8 +6699,9 @@
   and is refused after it. Metadata that parses today parses identically; the
   only thing that changes is what the Studio object designer teaches an author to
   write. The repeater now offers `label`, `value`, `color` and `description` —
-  exactly `SelectOptionSchema`'s authorable keys minus `visibleWhen`, which is a
-  CEL predicate rather than a repeater text input.
+  four of `SelectOptionSchema`'s six authorable keys. `default` and
+  `visibleWhen` are both unoffered; the latter because it is a CEL predicate
+  rather than a repeater text input, not because it is the only key withheld.
 
   **Why remove rather than declare.** The route rests on a premise measured for
   the FIELD-option surface rather than inherited from #5016, which measured the