crypt32/tests: Delete WineTest registry key when tests are complete

[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
https://testbot.winehq.org/JobDetails.pl?Key=17004

Your paranoid android.


=== w864 (64 bit store) ===
store.c:2603: Test failed: CertAddCertificateContextToStore failed
store.c:2604: Test failed: Unexpected cert3
store: unhandled exception c0000005 at 000000000044DAD6