tests: Remove unneeded assert.h includes.

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
http://testbot.winehq.org/JobDetails.pl?Key=14554

Your paranoid android.


=== WNT4WSSP6 (32 bit autocomplete) ===
autocomplete.c:249: Test failed: CoCreateInstance(&CLSID_ACLMulti, NULL, CLSCTX_INPROC, &IID_IEnumString, (LPVOID *)&obj) failed: 80040154