Remove installed python for force installation (#4807)
## Summary
Currently `uv python install` does not respect `--force` reinstallation,
the downloading process is just skipped if the installation existed.
```
$ uv python install 3.12
Looking for installation Python 3.12 (any-3.12-any-any-any)
Downloading cpython-3.12.3-windows-x86_64-none
Installed Python 3.12.3 to C:\Users\jo\AppData\Roaming\uv\data\python\cpython-3.12.3-windows-x86_64-none
Installed 1 installation in 6s
$ uv python install --force 3.12
Looking for installation Python 3.12 (any-3.12-any-any-any)
Found installed installation `cpython-3.12.3-windows-x86_64-none` that satisfies Python 3.12
Downloading cpython-3.12.3-windows-x86_64-none
Installed 1 installation in 0s
```
## Test Plan
```
$ uv python install 3.12
Looking for installation Python 3.12 (any-3.12-any-any-any)
Downloading cpython-3.12.3-windows-x86_64-none
Installed Python 3.12.3 to C:\Users\jo\AppData\Roaming\uv\data\python\cpython-3.12.3-windows-x86_64-none
Installed 1 installation in 6s
$ uv python install --force 3.12
Looking for installation Python 3.12 (any-3.12-any-any-any)
Found installed installation `cpython-3.12.3-windows-x86_64-none` that satisfies Python 3.12
Removing installed installation `cpython-3.12.3-windows-x86_64-none`
Downloading cpython-3.12.3-windows-x86_64-none
Installed Python 3.12.3 to C:\Users\jo\AppData\Roaming\uv\data\python\cpython-3.12.3-windows-x86_64-none
Installed 1 installation in 7s
```
