windowscodecs: Fix leak in test_QueryCapability.

[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=7580

Your paranoid android.


=== wvistau64 (32 bit tiffformat) ===
tiffformat.c:245: Test failed: CreateDecoderFromStream error 0x88982f8b
tiffformat: unhandled exception c0000005 at 0EEE3AA7

=== w2008s64 (32 bit tiffformat) ===
tiffformat.c:245: Test failed: CreateDecoderFromStream error 0x88982f8b
tiffformat: unhandled exception c0000005 at 0EEE3AA7

=== w7u (32 bit tiffformat) ===
tiffformat.c:245: Test failed: CreateDecoderFromStream error 0x88982f8b
tiffformat: unhandled exception c0000005 at 0EEE3AA7

=== w8 (32 bit tiffformat) ===
tiffformat: unhandled exception c0000005 at 0042395C

=== wvistau64 (64 bit tiffformat) ===
No test summary line found

=== w2008s64 (64 bit tiffformat) ===
No test summary line found