swift234

Remove two runs of the passes in AddSSAPasses.

I measure around a 10% reduction in compile times of release no-assert
builds of the stdlib and StdlibUnitTest.

For release + debug-swift builds, I see 20% reduction in stdlib compile
time.

I saw no reproducible regressions in the benchmarks, and a few
improvements.

There is a small (0.1%) reduction in the libswiftCore.dylib size.

Being able to remove these is a consequence of the reordering that
happened in e50daa6.