fix lint warnings

Author: fchapoton

src/sage/combinat/tableau.py

@@ -8133,7 +8133,6 @@ def __iter__(self):
 
             yield self.element_class(self, tableau)
 
-
     def list(self):
         r"""
         Return a list of the standard Young tableaux of the specified shape.

src/sage/graphs/matching_covered_graph.py

@@ -2661,7 +2661,6 @@ def remove_loops(self, vertices=None):
             raise TypeError(f'\'{vertices.__class__.__name__}\' '
                             'object is not iterable')
 
-
     @doc_index('Miscellaneous methods')
     def update_matching(self, matching):
         r"""