netfilter: nf_flowtable: fix documentation

In the flowtable documentation there is a missing semicolon, the command
as is would give this error:

    nftables.conf:5:27-33: Error: syntax error, unexpected devices, expecting newline or semicolon
                    hook ingress priority 0 devices = { br0, pppoe-data };
                                            ^^^^^^^
    nftables.conf:4:12-13: Error: invalid hook (null)
            flowtable ft {
                      ^^

Fixes: 19b351f1 ("netfilter: add flowtable documentation")
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Documentation/networking/nf_flowtable.txt

@@ -76,7 +76,7 @@ flowtable and add one rule to your forward chain.
 
         table inet x {
 		flowtable f {
-			hook ingress priority 0 devices = { eth0, eth1 };
+			hook ingress priority 0; devices = { eth0, eth1 };
 		}
                 chain y {
                         type filter hook forward priority 0; policy accept;