Remove bogus ATTRIBUTE_NONNULL from virFirewallAddRuleFull

The virFirewallAddRuleFull method originally had a single
compulsory virFirewallQueryCallback parameter. During dev
work though the ignoreErrors parameter was added and the
callback parameter made optional. The ATTRIBUTE_NONNULL
annotation was never removed though.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

src/util/virfirewall.h

@@ -59,7 +59,7 @@ virFirewallRulePtr virFirewallAddRuleFull(virFirewallPtr firewall,
                                           virFirewallQueryCallback cb,
                                           void *opaque,
                                           ...)
-    ATTRIBUTE_NONNULL(3) ATTRIBUTE_SENTINEL;
+    ATTRIBUTE_SENTINEL;
 
 void virFirewallRemoveRule(virFirewallPtr firewall,
                            virFirewallRulePtr rule);