fix: Backend Use Nacos cause OutOfMemoryError

[AYue-94]

What type of PR is this?

Bug.

What this PR does / why we need it?

When configcenter use nacos, remove sermant reconnect logic, because nacos will reconnect by itself.

Which issue(s) this PR fixes？

Fixes #1613

Does this PR introduce a user-facing change?

No

Checklist

• [x] Make sure there is a GitHub_issue related with this PR before you start working on it.
• [x] Make sure you have squashed your change to one single commit.
• [x] GitHub Actions works fine in this PR.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Flag	Coverage Δ	Complexity Δ
unittests	43.35% <100.00%> (+0.09%)	182.00 <0.00> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ	Complexity Δ
...rvice/dynamicconfig/nacos/NacosBufferedClient.java	52.45% <100.00%> (+6.40%)	0.00 <0.00> (ø)
...java/io/sermant/backend/service/ConfigService.java	28.87% <ø> (+0.98%)	0.00 <0.00> (ø)

... and 28 files with indirect coverage changes

[lilai23]

please use our pr template to describe this pr

[AYue-94]

fixed