DOC: Fix minor typo in docstring (pandas-dev#25285)

Author: elcombato

pandas/core/frame.py

@@ -5761,9 +5761,9 @@ def stack(self, level=-1, dropna=True):
         Notes
         -----
         The function is named by analogy with a collection of books
-        being re-organised from being side by side on a horizontal
+        being reorganized from being side by side on a horizontal
         position (the columns of the dataframe) to being stacked
-        vertically on top of of each other (in the index of the
+        vertically on top of each other (in the index of the
         dataframe).
 
         Examples