fix: Remove redundant instance requirement

[linesthatinterlace]

This PR removes a redundant instance requirement from Std.instIrreflLtOfIsPreorderOfLawfulOrderLT.

[linesthatinterlace]

I haven't submitted a bug for this - I can do if it seems necessary but it is such a small change I am hoping that won't be necessary.

[datokrat]

No, no need for a bug ticket, this is sufficient. Not sure what broke in "Linux Lake"; perhaps retriggering will help?

[TwoFX]

This is due to #10922 landing, so -Werror is now enabled on all PRs. Merging master should help.

[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 e71d0abc7ddb2c9da37e91b88fd2be2a903601c7 --onto efbbb0b230ce95653d25b59c83fd24a51a8bf363. You can force Mathlib CI using the force-mathlib-ci label. (2025-10-24 16:13:27)

[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 e71d0abc7ddb2c9da37e91b88fd2be2a903601c7 --onto d3dda9f6d4428a906c096067ecb75e432afc4615. You can force reference manual CI using the force-manual-ci label. (2025-10-24 16:13:28)

[linesthatinterlace]

I can't add the changelog label myself.

[TwoFX]

Try commenting changelog-library.

[linesthatinterlace]

changelog-library

[datokrat]

Thanks, good catch!