Keep the instructions for the Windows standalone installer consistent across the README and the documentation. (#8125)
## Summary
This PR aims to align the instructions for installing the Windows
standalone installer in the README with the current documentation.
https://github.com/astral-sh/uv/blob/7bd0d97ce573e9fa428d2b0076d83976e772b3b7/docs/getting-started/installation.md?plain=1#L17-L21
## Test Plan
Only README is modified and identical to the doc, so not tested.