Mod: update the comments in registy directory

[zouyx]

What this PR does:

• update the comments in registy directory

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-commenter]

Codecov Report

Merging #589 into develop will decrease coverage by 0.11%.
The diff coverage is 50.00%.

@@             Coverage Diff             @@
##           develop     #589      +/-   ##
===========================================
- Coverage    67.39%   67.28%   -0.12%     
===========================================
  Files          190      188       -2     
  Lines         9915     9854      -61     
===========================================
- Hits          6682     6630      -52     
+ Misses        2579     2573       -6     
+ Partials       654      651       -3     

Impacted Files	Coverage Δ
config_center/configuration_listener.go	0.00% <ø> (ø)
registry/consul/listener.go	81.25% <ø> (ø)
registry/consul/registry.go	43.83% <0.00%> (ø)
registry/directory/directory.go	80.11% <ø> (ø)
registry/etcdv3/listener.go	72.34% <ø> (ø)
registry/etcdv3/registry.go	73.13% <ø> (ø)
registry/kubernetes/listener.go	72.34% <ø> (ø)
registry/kubernetes/registry.go	67.30% <ø> (ø)
registry/nacos/listener.go	80.00% <ø> (ø)
registry/nacos/registry.go	58.42% <ø> (ø)
... and 26 more

---

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[fangyincheng]

LGTM