tailcfg: add omitempty to FilterRule.SrcBits
It's not used by recent clients, so even more reason to omit it.
@@ -572,7 +572,7 @@ type FilterRule struct {
// position is 32, as if the SrcIPs above were a /32 mask. For
// a "*" SrcIPs value, the corresponding SrcBits value is
// ignored.
- SrcBits []int
+ SrcBits []int `json:",omitempty"`
// DstPorts are the port ranges to allow once a source IP
// matches (is in the CIDR described by SrcIPs & SrcBits).
