Fix documentation typos for `uv build --build-constraint` flag (#7330)
Summary
This pull request fixes a typo in the --build-constraints flag, which
should be singular (--build-constraint). This update ensures consistency
across the documentation and prevents potential confusion for users.
Closes #7315
## Test Plan
The change was verified by reviewing the relevant documentation files
where the flag is referenced. No functional code changes were made, so
no additional testing is required beyond confirming the documentation
update.
## Tested
The change was tested by visually inspecting the updated documentation
to confirm that the typo has been corrected