Documentation: binding listeners must be IP.

[hexfusion]

ref: #6336, #9575

[gyuho]

Can we add more details? We can just say something like https://github.com/coreos/etcd/blob/master/Documentation/upgrades/upgrade_3_2.md#change-in---listen-peer-urls-and---listen-client-urls.

[hexfusion]

Yeah makes sense I found that after the fact. Will update to reflect versions.

[xiang90]

lgtm in general.

[hexfusion]

@gyuho updated, thanks.

[codecov-io]

Codecov Report

Merging #9638 into master will decrease coverage by 0.13%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #9638      +/-   ##
=========================================
- Coverage   69.33%   69.2%   -0.14%     
=========================================
  Files         373     373              
  Lines       34427   34427              
=========================================
- Hits        23870   23824      -46     
- Misses       8867    8904      +37     
- Partials     1690    1699       +9

Impacted Files	Coverage Δ
pkg/transport/timeout_conn.go	80% <0%> (-20%)	⬇️
etcdserver/api/v3rpc/lease.go	70.93% <0%> (-8.14%)	⬇️
etcdctl/ctlv3/command/lease_command.go	65.34% <0%> (-5.95%)	⬇️
proxy/grpcproxy/watcher.go	89.79% <0%> (-4.09%)	⬇️
etcdserver/v2_server.go	80.76% <0%> (-3.85%)	⬇️
etcdserver/api/v3rpc/watch.go	70.88% <0%> (-3.45%)	⬇️
etcdserver/v3_server.go	73.92% <0%> (-3.35%)	⬇️
rafthttp/msgappv2_codec.go	69.56% <0%> (-1.74%)	⬇️
pkg/netutil/netutil.go	68.85% <0%> (-1.64%)	⬇️
lease/leasehttp/http.go	58.08% <0%> (-1.48%)	⬇️
... and 8 more

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[gyuho]

lgtm thanks @hexfusion