fix: update legacy library deprecation warning to specify Willow release

[irfanuddinahmad]

Description

Replaces the vague phrase "In a future release" with the specific release name "In the Willow release" in the legacy libraries migration alert shown on the Legacy Libraries tab of Studio Home.

Before:

In a future release, legacy libraries will no longer be supported. ...

After:

In the Willow release, legacy libraries will no longer be supported. ...

Supporting information

• Closes [verawood] Legacy Libraries DEPR: Warnings in the UI #2876
• Flagged by @crathbun428 in the issue review (Apr 13, 2026)
• File: src/studio-home/tabs-section/messages.ts (alertDescriptionV1)

Test plan

• Navigate to Studio Home → Legacy Libraries tab
• Confirm the migration alert reads "In the Willow release, legacy libraries will no longer be supported."

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.61%. Comparing base (3f531d5) to head (7080b30).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3078   +/-   ##
=======================================
  Coverage   95.61%   95.61%           
=======================================
  Files        1391     1391           
  Lines       33075    33075           
  Branches     7680     7680           
=======================================
  Hits        31626    31626           
  Misses       1384     1384           
  Partials       65       65           

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[irfanuddinahmad]

Closing this PR as it no longer makes sense to merge.

This fix was intended for Verawood, where users would see the warning ahead of the Willow removal. However, Verawood's code freeze has already passed (May 1, 2026), so this can't land in Verawood.

In Willow, the legacy library pages that display this warning will be removed entirely (as part of openedx-platform#38056), so the warning would either never be seen or confusingly self-reference the current release.

The warnings added by openedx-platform#38225 and #2963 (merged March/April 2026) are sufficient for Verawood — the "in a future release" wording is acceptable given the context. Closing issue #2876 as done-enough.