fix: set default capacity for rate limiting in PushConsumerConfig

[sysulq]

Describe what this PR does / why we need it

Does this pull request fix one issue?

Describe how you did it

Describe how to verify it

Special notes for reviews

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 46.76%. Comparing base (43e3489) to head (2d57041).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/client/rocketmq/push_consumer.go	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1214      +/-   ##
==========================================
+ Coverage   46.71%   46.76%   +0.04%     
==========================================
  Files         236      236              
  Lines       13027    13026       -1     
==========================================
+ Hits         6086     6091       +5     
+ Misses       6481     6476       -5     
+ Partials      460      459       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.