fix(calico): Force good MTU

With wireguard it's suggested to set the MTU to 60 bytes less than the
general MTU of the interfaces. the general interfaces have a standard
MTU of 1500.

References:
https://projectcalico.docs.tigera.io/networking/mtu#determine-mtu-size

bootstrap/calico/release.yaml

@@ -24,6 +24,7 @@ spec:
       calicoNetwork:
         bgp: Enabled
         hostPorts: Enabled
+        mtu: 1440
         ipPools:
           - blockSize: 26
             cidr: 10.1.0.0/16