DOC: Fix typo in docstring (#14970)

Author: divergentdave

pandas/core/generic.py

@@ -690,7 +690,7 @@ def f(x):
     def rename_axis(self, mapper, axis=0, copy=True, inplace=False):
         """
         Alter index and / or columns using input function or functions.
-        A scaler or list-like for ``mapper`` will alter the ``Index.name``
+        A scalar or list-like for ``mapper`` will alter the ``Index.name``
         or ``MultiIndex.names`` attribute.
         A function or dict for ``mapper`` will alter the labels.
         Function / dict values must be unique (1-to-1). Labels not contained in