DOC: Improve documented types for merge (#48985)

Correct list of supported types in docs Remove block creating incorrect docs in merge Co-authored-by: Patrick Hoefler <61934744+phofl@users.noreply.github.com>

Author: bashtage

pandas/core/reshape/merge.py

@@ -152,10 +152,6 @@ def merge(
  return op.get_result(copy=copy)
 
 
-if __debug__:
- merge.__doc__ = _merge_doc % "\nleft : DataFrame"
-
-
 def _groupby_and_merge(by, left: DataFrame, right: DataFrame, merge_pieces):
  """
  groupby & merge; we are always performing a left-by type operation
@@ -232,8 +228,8 @@ def merge_ordered(
 
  Parameters
  ----------
- left : DataFrame
- right : DataFrame
+ left : DataFrame or named Series
+ right : DataFrame or named Series
  on : label or list
  Field names to join on. Must be found in both DataFrames.
  left_on : label or list, or array-like
@@ -245,10 +241,10 @@ def merge_ordered(
  left_on docs.
  left_by : column name or list of column names
  Group left DataFrame by group columns and merge piece by piece with
- right DataFrame.
+ right DataFrame. Must be None if either left or right are a Series.
  right_by : column name or list of column names
  Group right DataFrame by group columns and merge piece by piece with
- left DataFrame.
+ left DataFrame. Must be None if either left or right are a Series.
  fill_method : {'ffill', None}, default None
  Interpolation method for data.
  suffixes : list-like, default is ("_x", "_y")