Remove redundant usage of WITH_YAJL

As of commit 2a00ef6e71 which
was released in v5.2.0, we require YAJL to build the QEMU driver.

Remove the checks from code that requires the QEMU driver
or checks that also check for WITH_QEMU.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

tests/qemuagenttest.c

@@ -1426,11 +1426,6 @@ mymain(void)
 {
     int ret = 0;
 
-#if !WITH_YAJL
-    fputs("libvirt not compiled with JSON support, skipping this test\n", stderr);
-    return EXIT_AM_SKIP;
-#endif
-
     if (qemuTestDriverInit(&driver) < 0)
         return EXIT_FAILURE;