Disable SSL in Git commands for `--allow-insecure-host` (#11210)
## Summary
Closes https://github.com/astral-sh/uv/issues/11176.
## Test Plan
- Created a self-signed certificate.
- Ran `openssl s_server -cert cert.pem -key key.pem -WWW -port 8443`.
- Verified that `cargo run pip install
git+https://localhost:8443/repo.git` failed with:
```
error: Git operation failed
Caused by: failed to fetch into: /Users/crmarsh/.cache/uv/git-v0/db/0773914b3ec4a56e
Caused by: process didn't exit successfully: `/usr/bin/git fetch --force --update-head-ok 'https://localhost:8443/repo.git' '+HEAD:refs/remotes/origin/HEAD'` (exit status: 128)
--- stderr
fatal: unable to access 'https://localhost:8443/repo.git/': SSL certificate problem: self signed certificate
```
- Verified that `cargo run pip install
git+https://localhost:8443/repo.git --allow-insecure-host
https://localhost:8443` continued further.
