optimize: correct variable name typo in DeflaterUtil

[psxjoy]

• I have read the CONTRIBUTING.md guidelines.
• I have registered the PR changes.

Ⅰ. Describe what this PR did

correct variable name typo in DeflaterUtil

Ⅱ. Does this pull request fix one issue?

Not applicable.

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

Not applicable.

Ⅳ. Describe how to verify it

Not applicable.

Ⅴ. Special notes for reviews

Not applicable.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.20%. Comparing base (a977730) to head (52e5511).
⚠️ Report is 2 commits behind head on 2.x.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #7668      +/-   ##
============================================
- Coverage     61.40%   61.20%   -0.20%     
  Complexity      666      666              
============================================
  Files          1314     1314              
  Lines         49760    49760              
  Branches       5849     5849              
============================================
- Hits          30553    30454      -99     
- Misses        16474    16573      +99     
  Partials       2733     2733              

Files with missing lines	Coverage Δ
...apache/seata/compressor/deflater/DeflaterUtil.java	80.64% <100.00%> (ø)

... and 11 files with indirect coverage changes

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[slievrly]

LGTM