Mark `sync::sync_dry_run` test as requiring `python-managed` (#11415)
## Summary
Mark `sync::sync_dry_run` as requiring `python-managed`, as it fails
with system Python executables due to extraneous Python packages being
installed:
```
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Snapshot Summary ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Snapshot: sync_dry_run
Source: crates/uv/tests/it/sync.rs:6574
────────────────────────────────────────────────────────────────────────────────
Expression: snapshot
────────────────────────────────────────────────────────────────────────────────
-old snapshot
+new results
────────────┬───────────────────────────────────────────────────────────────────
5 5 │ Using CPython 3.12.[X] interpreter at: [PYTHON-3.12]
6 6 │ Would create virtual environment at: .venv
7 7 │ Resolved 2 packages in [TIME]
8 8 │ Would create lockfile at: uv.lock
9 │-Would download 1 package
10 │-Would install 1 package
11 │- + iniconfig==2.0.0
9 │+Would uninstall 1310 packages
10 │+ - a2wsgi==1.10.8
[…]
```
## Test Plan
```
cargo test --no-default-features --features=python,pypi,git
```