[3.12] gh-81479: For Help => IDLE Doc, stop double-spacing some lists. (GH-114168) (#114170)

This matches Firefox format.  Edge double-spaces non-simple
lists but I think it looks worse.
(cherry picked from commit e07a400c310ad3bdd72bb0ae401991af17435e4d)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>