[fix][client] Fix ConsumerStats.getRateMsgsReceived javadoc

[ahscuml]

• [doc] easy doc fix

• doc

• doc-required

• doc-not-needed

• doc-complete

[github-actions]

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- [ ] `doc-not-needed` <!-- Your PR changes do not impact docs -->
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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.26%. Comparing base (2a5aa44) to head (ad72fce).
Report is 890 commits behind head on master.

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #21618       +/-   ##
=============================================
+ Coverage     36.73%   74.26%   +37.53%     
- Complexity    12195    34383    +22188     
=============================================
  Files          1715     1943      +228     
  Lines        131087   146973    +15886     
  Branches      14317    16191     +1874     
=============================================
+ Hits          48155   109155    +61000     
+ Misses        76543    29381    -47162     
- Partials       6389     8437     +2048     

Flag	Coverage Δ
inttests	27.32% <ø> (+3.12%)	⬆️
systests	24.43% <ø> (-0.58%)	⬇️
unittests	73.62% <ø> (+41.95%)	⬆️

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Files with missing lines	Coverage Δ
...va/org/apache/pulsar/client/api/ConsumerStats.java	0.00% <ø> (ø)

... and 1644 files with indirect coverage changes