proposal: remove _execute_compiled()

proposal: remove _execute_compiled()

this isn't used internally and only allows execute(stmt.compile())
to work, which is not something I want to support.

Since people are definitely using this [1] we might want to think about
either deprectation or having a recipe for people who really want
to still do this

[1] https://github.com/sqlalchemy/sqlalchemy/discussions/11108?converting=1

Change-Id: I5f0fe800e31aac052926cebe9206763eef9a804c