selftests/bpf: Remove unused struct 'libcap'

'libcap' is unused since commit b1c2768a ("bpf: selftests: Remove libcap
usage from test_verifier"). Remove it.
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240602234112.225107-4-linux@treblig.org

tools/testing/selftests/bpf/test_verifier.c

@@ -1237,11 +1237,6 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
 	fixup_prog_kfuncs(prog, fd_array, test->fixup_kfunc_btf_id);
 }
 
-struct libcap {
-	struct __user_cap_header_struct hdr;
-	struct __user_cap_data_struct data[2];
-};
-
 static int set_admin(bool admin)
 {
 	int err;