Add missing period to get_dummies docs (#21277)

Author: adamjstewart

pandas/core/reshape/reshape.py

@@ -725,7 +725,7 @@ def get_dummies(data, prefix=None, prefix_sep='_', dummy_na=False,
     ----------
     data : array-like, Series, or DataFrame
     prefix : string, list of strings, or dict of strings, default None
-        String to append DataFrame column names
+        String to append DataFrame column names.
         Pass a list with length equal to the number of columns
         when calling get_dummies on a DataFrame. Alternatively, `prefix`
         can be a dictionary mapping column names to prefixes.