[libc] Clean up some unused includes (#220038)

The `CMakeLists.txt` for these already reflect the correct dependencies
(e.g. `libc/startup/linux/x86_64/tls.cpp` depends on
`libc.config.app_h`, not `do_start`). I was adding some Bazel rules for
libc entrypoints and saw these unused deps.

GitOrigin-RevId: 52774ef910fe941d90b5594ce578e459fbb108a8