kernel32/tests: Remove unused strings (Clang)

[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=10564

Your paranoid android.


=== wvistau64 (32 bit file) ===
file.c:365: Test failed: attributes of file "testfile.xxx" are 0x0820

=== wvistau64 (64 bit file) ===
file.c:365: Test failed: attributes of file "testfile.xxx" are 0x0820