gh-93692: remove "build finished successfully" message from setup.py (GH-93693)

The message was only emitted when the build succeeded _and_ there were
missing modules.
(cherry picked from commit ab077d1e17032f84514292ae3fb8dee9bcfd2ce9)

Co-authored-by: Erlend Egeberg Aasland <erlend.aasland@protonmail.com>