fix(lazy_imports): type import_map as Mapping to stay under the LIT001 budget

The revert restored the dict annotation that #39121 had loosened to Mapping,
and the LIT001 ceiling has been ratcheted down since, so the gate rejected the
one reintroduced hit. Annotation only, no behavior change.

litellm/_lazy_imports.py

@@ -229,7 +229,7 @@ def _module_attribute(module: ModuleType, attr_name: str) -> object:
     return attribute["value"]
 
 
-def _generic_lazy_import(name: str, import_map: dict[str, tuple[str, str]], category: str) -> object:
+def _generic_lazy_import(name: str, import_map: Mapping[str, tuple[str, str]], category: str) -> object:
     """
     Generic function that handles lazy importing for most attributes.