docs: update chart readme

[luckymrwang]

What type of PR is this?

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/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage

/kind documentation

What this PR does / why we need it:

yurt-tunnel-agent and yurt-tunnel-server will be moved in raven.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

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In response to this:

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage
/kind documentation

What this PR does / why we need it:

yurt-tunnel-agent and yurt-tunnel-server will be moved in raven.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

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[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[codecov]

Codecov Report

Merging #1305 (38860a6) into master (b7eff36) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1305   +/-   ##
=======================================
  Coverage   53.59%   53.59%           
=======================================
  Files         102      102           
  Lines       12749    12749           
=======================================
  Hits         6833     6833           
  Misses       5362     5362           
  Partials      554      554           

Flag	Coverage Δ
unittests	53.59% <ø> (ø)

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[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: luckymrwang, rambohe-ch

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• OWNERS [rambohe-ch]

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[rambohe-ch]

/lgtm