fix: Dynamic update rate limit config with wrong value

[weiliu1031]

pr: #29901
when apply dynamic config changes, we should format the value to proper unit
This PR fix update rate limit config with wrong value.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c0b711e) 82.13% compared to head (c47e547) 82.14%.
Report is 8 commits behind head on 2.3.

Additional details and impacted files

@@           Coverage Diff           @@
##              2.3   #29902   +/-   ##
=======================================
  Coverage   82.13%   82.14%           
=======================================
  Files         833      833           
  Lines      120080   120080           
=======================================
+ Hits        98632    98635    +3     
- Misses      18222    18224    +2     
+ Partials     3226     3221    -5     

Files	Coverage Δ
internal/proxy/multi_rate_limiter.go	90.59% <100.00%> (-1.29%)	⬇️

... and 12 files with indirect coverage changes

[congqixia]

/lgtm

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: congqixia, weiliu1031

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