fix: export symbols needed by Verso

[david-christiansen]

Verso needed a symbol that was unexported - this exposes it again.

[leanprover-community-mathlib4-bot]

Mathlib CI status (docs):

• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase 6a4159c4a792ed2e74f20aecf73974dc3e314e2c --onto 8acdafd5b3957382c02779ada451c14da44e2aca. (2024-07-31 13:52:34)

[kim-em]

No opinion on the solution, but unless someone objects I will make sure this is in in time for v4.11.0-rc1.

[david-christiansen]

Thanks! We should do a stage0 update before rc1 as well, because otherwise Verso will only work on stage2 builds from master (the exported symbols are determined by the prior stage's compiler).

[david-christiansen]

Stage0 update triggered.