Merge pull request #7545 from neirbowj/frame_to_excel_docstring

DOC: Use correct, non-deprecated arg name

Author: jorisvandenbossche

pandas/core/frame.py

@@ -1166,7 +1166,7 @@ def to_excel(self, excel_writer, sheet_name='Sheet1', na_rep='',
             Missing data representation
         float_format : string, default None
             Format string for floating point numbers
-        cols : sequence, optional
+        columns : sequence, optional
             Columns to write
         header : boolean or list of string, default True
             Write out column names. If a list of string is given it is