fix: add table variant for `require.git` field in `lakefile.toml` schema

[maxwell3025]

This PR corrects the JSON Schema at src/lake/schemas/lakefile-toml-schema.json to allow the table variant of the require.git field in lakefile.toml as specified in the reference.

Closes #11535

[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 2ca3bc28590c5c33f755d3bd18252f25ea266266 --onto 455fd0b4488e2adc85f825a52e2ee7d944a5740a. You can force Mathlib CI using the force-mathlib-ci label. (2025-12-07 01:44:22)
• ✅ Mathlib branch lean-pr-testing-11536 has successfully built against this PR. (2025-12-07 16:38:29) View Log
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• ✅ Mathlib branch lean-pr-testing-11536 has successfully built against this PR. (2025-12-08 22:41:13) View Log

[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 2ca3bc28590c5c33f755d3bd18252f25ea266266 --onto d3dda9f6d4428a906c096067ecb75e432afc4615. You can force reference manual CI using the force-manual-ci label. (2025-12-07 01:44:23)
• ❗ Reference manual CI can not be attempted yet, as the nightly-testing-2025-12-07 tag does not exist there yet. We will retry when you push more commits. If you rebase your branch onto nightly-with-manual, reference manual CI should run now. You can force reference manual CI using the force-manual-ci label. (2025-12-07 15:34:31)

[maxwell3025]

I don't have the permissions necessary to add labels, but this should have the label changelog-server