Write __exit__ for ImageProvider

Author: conjuncts

marker/providers/image.py

@@ -46,4 +46,7 @@ def get_page_lines(self, idx: int) -> List[Line]:
         return self.page_lines[idx]
 
     def get_page_refs(self, idx: int) -> List[Reference]:
-        return []
+        return []
+    
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        pass # images need to survive