gh-89158: Add some REPL secondary prompt markers (GH-93073)

This fixes an issue on tutorial/classes.rst section 9.4 where the example "class Warehouse"
was truncated when pressing the >>> button to hide the prompts and output.
(cherry picked from commit 88f0d0c1e8fdda036f3f64b0048911ba28ce7f06)

Co-authored-by: Nicolas Haller <nicolas@haller.im>