Fix windows install hook

Closes iterative/dvc#7700

Author: daavoo

scmrepo/git/__init__.py

@@ -242,7 +242,7 @@ def install_hook(
         self.hooks_dir.mkdir(exist_ok=True)
         hook = self.hooks_dir / name
 
-        directive = f"#!{shutil.which(interpreter)}"
+        directive = f"#!{shutil.which(interpreter) or '/bin/sh' }"
         hook.write_text(f"{directive}\n{script}\n", encoding="utf-8")
         hook.chmod(0o777)