prepare to release 6.0.2

[leizhiyuan]

rpc 5.5.4
sofaboot 3.1.4
sofa starter 6.0.2

Motivation:

Explain the context, and why you're making that change.
To make others understand what is the problem you're trying to solve.

Modification:

Describe the idea and modifications you've done.

Result:

Fixes #.

If there is no issue then describe the changes introduced by this PR.

[codecov-io]

Codecov Report

Merging #193 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #193   +/-   ##
=========================================
  Coverage     62.55%   62.55%           
  Complexity      497      497           
=========================================
  Files            60       60           
  Lines          1912     1912           
  Branches        334      334           
=========================================
  Hits           1196     1196           
  Misses          503      503           
  Partials        213      213

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