ALTER ROUTINE triggers the events ddl_command_start and ddl_command_end,
and DROP ROUTINE triggers sql_drop, ddl_command_start and
ddl_command_end, but this was not mention on the matrix table.

Reported-by: Leslie Lemaire
Discussion: https://postgr.es/m/164647533363.646.5802968483136493025@wrigleys.postgresql.org
Backpatch-through: 11