Fix documentation for python platform

[neumann-nico]

Summary

The option --platform for uv pip compile was added in #3111 and was later renamed to --python-platform #3146.
This PR updates the documentation such that the listed option is working again.

Test Plan

❯ uv --version
uv 0.1.37 (645d0399f 2024-04-23)

Before:

❯ uv pip compile requirements.in --platform=linux
error: unexpected argument '--platform' found

  tip: to pass '--platform' as a value, use '-- --platform'

Usage: uv pip compile <SRC_FILE>...

For more information, try '--help'.

After:

❯ uv pip compile requirements.in --python-platform=linux
Resolved 1 package in 215ms
# This file was autogenerated by uv via the following command:
#    uv pip compile requirements.in --python-platform=linux
uv==0.1.37

[zanieb]

Thank you!

[charliermarsh]

Tyvm.