Avoid canonicalizing executables on Windows (#5446)

## Summary

If you have an executable path on a network share path (like
`\\some-host\some-share\...\python.exe`), canonicalizing it adds the
`\\?` prefix, but dunce cannot safely strip it.

This PR changes the Windows logic to avoid canonicalizing altogether. We
don't really expect symlinks on Windows, so it seems unimportant to
resolve them.

Closes: https://github.com/astral-sh/uv/issues/5440.

crates/uv-virtualenv/src/virtualenv.rs

@@ -76,7 +76,7 @@ pub(crate) fn create(
                 interpreter.sys_base_prefix().join("python.exe")
             }
         } else {
-            uv_fs::canonicalize_executable(interpreter.sys_executable())?
+            interpreter.sys_executable().to_path_buf()
         }
     } else {
         unimplemented!("Only Windows and Unix are supported")