Update source/manual/how-tos/ipv6_fb.rst

source/manual/how-tos/ipv6_fb.rst

@@ -135,7 +135,7 @@ Step 4 - setup Firewall rules
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 All clients should now have a proper IPv6 address (actually more than one), know their DNS servers and their upstream router.
-All thats left to do is adding the appropriate firewall rules. 
+All that is left to do is adding the appropriate firewall rules for incoming traffic.
 
 By default outgoing traffic should already be possible but traffic from the Internet to the internal server needs a firewall rule.
 There are different philosophies on how to manage firewall rules. Just use a similar strategy as with your IPv4 setup so rule management