docs(whats-new-23): add 2.3.1 cascade fix bullet; refresh releases link

[MilagrosMarin]

Two small follow-ups on whats-new-23.md after v2.3.1 shipped.

Changes

Cascade multi-part-master fix (datajoint-python#1484) — added as the third bullet under "Changes in 2.3.1". The section listed strict_provenance removal, Python 3.14, and the GC fix, but the multi-part-master cascade fix — a silent-integrity path where two Parts of the same Master could leave the Master with rows that should have been deleted — was omitted despite being a v2.3.1 highlight in the release announcement.

Stale release-notes link — [Release Notes (v2.3.0)](.../releases) in See Also updated to [Release Notes (v2.3.1)](.../releases/tag/v2.3.1).

Docs-only.

[dimitri-yatsenko]

The cascade-fix bullet and the v2.3.1 release-link refresh are both great — please keep those.

One trim: I'd drop the sentence "Invalid part_integrity values now raise ValueError." Two reasons:

1. It's assumed behavior. ValueError is the expected result for an invalid enum-like argument (and intentionally so — we reserve DataJointError for DataJoint-specific logic, so a bad argument value correctly raises the stdlib ValueError). It doesn't need a callout.
2. More importantly, "now" mis-dates it. Table.delete() has raised ValueError on invalid part_integrity since 2.3.0 — the check shipped in cabdb744 (an ancestor of v2.3.0, table.py:841-842). What 2.3.1 (179c39be) actually did was replicate the same validation into Diagram.cascade and add a drop() variant. So as a What's New in 2.3.1 line it reads as a change that, for delete(), isn't one.

Same reasoning underlies the suggestion on #213. Everything else in this PR is good to merge once that sentence is out.

[MilagrosMarin]

Thanks — you're right that the ValueError line mis-dates the delete() side (the raise was in 2.3.0, not new in 2.3.1) and doesn't add reader value alongside the values table. Dropped in 07f3818. Ready for another look.

[MilagrosMarin]

Good catch — you're right, the page covers the whole 2.3 line. Pushed 9b4a903: text is now 'Release Notes (2.3.x)' pointing to /releases so it stays valid across 2.3.1, 2.3.2, etc.

[dimitri-yatsenko]

LGTM. The ValueError callout is dropped (it restated assumed behavior and mis-dated a check that shipped in 2.3.0), and the cascade-fix bullet reads well. Generalizing the link to 2.3.x → /releases is a good call — stable across the series and avoids pointing at a tag before it's published.