DEV: Remove ignore Ruff rule RET503

pypdf/_page.py

@@ -1087,6 +1087,7 @@ def _merge_page(
                 return self._merge_page_writer(
                     page2, page2transformation, ctm, over, expand
                 )
+                return None
         except (AssertionError, AttributeError):
             pass
 
@@ -1179,6 +1180,7 @@ def _merge_page(
         self.replace_contents(ContentStream(new_content_array, self.pdf))
         self[NameObject(PG.RESOURCES)] = new_resources
         self[NameObject(PG.ANNOTS)] = new_annots
+        return None
 
     def _merge_page_writer(
         self,

pypdf/_writer.py

@@ -2240,6 +2240,7 @@ def clean_forms(
 
             clean(content, images, forms, text_filters)
             page.replace_contents(content)
+        return [], []  # type: ignore
 
     def remove_images(
         self,
@@ -3213,6 +3214,7 @@ def find_outline_item(
                 o = cast(TreeObject, o["/Next"])
             else:
                 return None
+        return None  # This line may be unreachable?
 
     def find_bookmark(
         self,

pyproject.toml

@@ -179,7 +179,6 @@ ignore = [
     "PT014",   # Ruff bug: Duplicate of test case at index 1 in `@pytest_mark.parametrize`
     "PTH123",  # `open()` should be replaced by `Path.open()`
     "PYI042",  # Type alias `mode_str_type` should be CamelCase
-    "RET503",  # Missing explicit `return` at the end of function able to return non-`None` value
     "RUF001",  # Detect confusable Unicode-to-Unicode units. Introduces bugs
     "RUF002",  # Detect confusable Unicode-to-Unicode units. Introduces bugs
     "S101",    # Use of `assert` detected