bugfix: fix ProtocolV1SerializerTest failed

[slievrly]

• I have registered the PR changes.

Ⅰ. Describe what this PR did

optimize ProtocolV1SerializerTest failed

Ⅱ. Does this pull request fix one issue?

fixes #6277

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-commenter]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (3351fcf) 51.07% compared to head (f4f3831) 51.10%.
Report is 4 commits behind head on 2.x.

❗ Current head f4f3831 differs from pull request most recent head b2b9b7d. Consider uploading reports for the commit b2b9b7d to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #6278      +/-   ##
============================================
+ Coverage     51.07%   51.10%   +0.02%     
+ Complexity     5097     5096       -1     
============================================
  Files           918      918              
  Lines         32031    32038       +7     
  Branches       3865     3866       +1     
============================================
+ Hits          16361    16373      +12     
+ Misses        14097    14088       -9     
- Partials       1573     1577       +4     

Files	Coverage Δ
.../io/seata/core/rpc/netty/v1/ProtocolV1Decoder.java	14.54% <33.33%> (+4.12%)	⬆️

... and 3 files with indirect coverage changes

[funky-eyes]

LGTM