swift234

Revert "[Sema] Improve diagnostics for witness mismatches against @objc protocols." and "Improve diagnostics for selector collisions with @objc optional requirements."

This reverts commits 46269299cd40252f6be69cf30db3dce3a9f5252a
and 27279866ad40b46270f376fe95e9488ecff7db62
and c826a408dd35764ca23d0838f5aa1475ec0ad3af.

The changes broke test bots, including
https://ci.swift.org/job/oss-swift-package-osx/1348/