add get_exist_path to systemctl3.pyi

Signed-off-by: ladyrick <[email protected]>

types/systemctl3.pyi

@@ -117,6 +117,7 @@ def unit_name_unescape(text: str) -> str: ...
 def is_good_root(root: Optional[str]) -> bool: ...
 def os_path(root: Optional[str], path: str) -> str: ...
 def path_replace_extension(path: str, old: str, new: str) -> str: ...
+def get_exist_path(paths: List[str]) -> Optional[str]: ...
 def get_PAGER() -> List[str]: ...
 def os_getlogin() -> str: ...
 def get_runtime_dir() -> str: ...