Remove investigative code for can't-reattach-to-shared-memory errors.

Revert commits 23078689, 73042b8d, ce07aff4, f7df8043, 6ba0cc4b,
eb16011f, 68e7e973, 63ca350e.  We still have a problem here, but
somebody who's actually a Windows developer will need to spend time
on it.

Discussion: https://postgr.es/m/25495.1524517820@sss.pgh.pa.us