DOC: fix wrongly placed versionadded (#16702)

Author: jorisvandenbossche

pandas/core/strings.py

@@ -611,11 +611,12 @@ def str_extract(arr, pat, flags=0, expand=None):
     flags : int, default 0 (no flags)
         re module flags, e.g. re.IGNORECASE
 
-    .. versionadded:: 0.18.0
     expand : bool, default False
         * If True, return DataFrame.
         * If False, return Series/Index/DataFrame.
 
+        .. versionadded:: 0.18.0
+
     Returns
     -------
     DataFrame with one row for each subject string, and one column for