[ISSUE #996] Remove unused code

[Cshiyuan]

Please provide issue(s) of this PR:
Fixes #996

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• Does not have any user-facing changes. This may include API changes, behavior changes, performance improvements, etc.

[polaris-test-bot]

2023-03-18 15:44:43: =========TEST START==========
2023-03-18 15:45:09: Pre-Merge check success! Now we will perform a full automated test which is expected to take 2 hours, thank you for your patience.
2023-03-18 15:59:30: [STANDALONE VERSION]PR autotest PASSED! We executed 20 test cases and 20 were passed. You can see test report in https://polaris-opentest-1306863770.cos.ap-guangzhou.myqcloud.com/pr1280995134/sta/qta-report.html
2023-03-18 15:59:34: [CLUSTER VERSION] PR autotest PASSED! We executed 20 test cases and 20 were passed. You can see test report in https://polaris-opentest-1306863770.cos.ap-guangzhou.myqcloud.com/pr1280995134/clu/qta-report.html
2023-03-18 15:59:38: [KUBENETES VERSION]PR autotest PASSED! We executed 20 test cases and 20 were passed. You can see test report in https://polaris-opentest-1306863770.cos.ap-guangzhou.myqcloud.com/pr1280995134/k8s/qta-report.html

[codecov]

Codecov Report

Merging #1020 (7856279) into main (30811f9) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1020      +/-   ##
==========================================
- Coverage   57.37%   57.35%   -0.02%     
==========================================
  Files         191      191              
  Lines       34409    34401       -8     
==========================================
- Hits        19742    19731      -11     
  Misses      12096    12096              
- Partials     2571     2574       +3     

Impacted Files	Coverage Δ
service/ratelimit_config.go	63.92% <ø> (+0.26%)	⬆️

... and 4 files with indirect coverage changes

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