clar: stop including shellapi.h unnecessarily

The `shellapi.h` header was included as of
clar-test/clar@136e763211aa, to have
`SHFileOperation()` declared so that it could be called.

However, clar-test/clar@5ce31b69b525 removed
that call, and therefore that `#include <shellapi.h>` is unnecessary.

It is also unwanted in Git because this project uses a subset of Git for
Windows' SDK in its CI builds that (for bandwidth reasons) excludes tons
of header files, including `shellapi.h`.

So let's remove it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

t/unit-tests/clar/clar.c

@@ -21,7 +21,6 @@
 #ifdef _WIN32
 #	include <windows.h>
 #	include <io.h>
-#	include <shellapi.h>
 #	include <direct.h>
 
 #	define _MAIN_CC __cdecl