Revert "[Flang][Parser] Add missing dependencies to CMakeLists.txt (#77483)"

This reverts commit cc53ec82.

This commit hasn't accomplished anything. The original issue was that
`DumpTree`, when called from lowering, caused linker errors due to some
directive-naming functions being absent. Adding FrontendOpenMP to the
parser library didn't fix that problem, and according to the notes in
PR #77483, calling `DumpTree` from lowering isn't really supported.