qemu: Remove coverity[negative_returns] annotation

It was added in commit 6c2e4c38
so that Coverity would not complain about passing -1 to
qemuDomainDetachThisHostDevice(), but the function in question
has changed since and so the annotation doesn't apply anymore.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>

src/qemu/qemu_hotplug.c

@@ -5007,7 +5007,6 @@ qemuDomainDetachNetDevice(virQEMUDriverPtr driver,
     detach = vm->def->nets[detachidx];
 
     if (virDomainNetGetActualType(detach) == VIR_DOMAIN_NET_TYPE_HOSTDEV) {
-        /* coverity[negative_returns] */
         ret = qemuDomainDetachThisHostDevice(driver, vm,
                                              virDomainNetGetActualHostdev(detach));
         goto cleanup;