chore: adjust pr-title check to enforce capitalization

[TwoFX]

This PR updates the pr-title CI check to enforce that the commit message does not start with a capital letter followed by a non-capital letter.

This should ensure that messages do not start with a capitalized word, but allow messages that start with an acronym.

[leanprover-community-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 1ce05b2a179eac8a902995c0caddc609c0169c49 --onto 705084d9ba258dec704af428d7ce2444525f9ffb. You can force Mathlib CI using the force-mathlib-ci label. (2025-10-31 07:21:19)

[leanprover-bot]

Reference manual CI status:

• ❗ Reference manual CI will not be attempted unless your PR branches off the nightly-with-manual branch. Try git rebase 1ce05b2a179eac8a902995c0caddc609c0169c49 --onto d3dda9f6d4428a906c096067ecb75e432afc4615. You can force reference manual CI using the force-manual-ci label. (2025-10-31 07:21:21)

[nomeata]

So feat: FunInd: don't crash would be disallowed now?

[nomeata]

I guess I'll just put In in front of component names

[TwoFX]

@nomeata Yes, I agree that this is unfortunate, I apologize for that. We could have a label to go back to the old rule on individual PRs. Would you use that?

[nomeata]

No, that's clearly overkill. I'll adapt.