fix restNum calculation in pop consumption mode

[ShadowySpirits]

fix #5842

[codecov-commenter]

Codecov Report

Merging #5843 (eee0346) into develop (98ebcef) will decrease coverage by 0.02%.
The diff coverage is 29.16%.

@@              Coverage Diff              @@
##             develop    #5843      +/-   ##
=============================================
- Coverage      42.41%   42.38%   -0.03%     
+ Complexity      8226     8216      -10     
=============================================
  Files           1060     1060              
  Lines          73417    73416       -1     
  Branches        9607     9605       -2     
=============================================
- Hits           31140    31118      -22     
- Misses         38352    38369      +17     
- Partials        3925     3929       +4     

Impacted Files	Coverage Δ
...rocketmq/broker/processor/PopMessageProcessor.java	36.58% <29.16%> (-0.10%)	⬇️
...e/rocketmq/store/ha/autoswitch/EpochFileCache.java	77.08% <0.00%> (-4.17%)	⬇️
...ache/rocketmq/broker/client/ConsumerGroupInfo.java	69.29% <0.00%> (-3.51%)	⬇️
.../org/apache/rocketmq/store/ha/DefaultHAClient.java	58.97% <0.00%> (-2.57%)	⬇️
...mq/store/ha/autoswitch/AutoSwitchHAConnection.java	70.00% <0.00%> (-2.44%)	⬇️
...a/org/apache/rocketmq/filter/util/BloomFilter.java	60.43% <0.00%> (-2.20%)	⬇️
...ache/rocketmq/proxy/common/ReceiptHandleGroup.java	65.30% <0.00%> (-2.05%)	⬇️
...mq/client/impl/consumer/RebalanceLitePullImpl.java	69.86% <0.00%> (-1.37%)	⬇️
.../org/apache/rocketmq/store/index/IndexService.java	59.00% <0.00%> (-1.00%)	⬇️
...ent/impl/consumer/DefaultLitePullConsumerImpl.java	69.37% <0.00%> (-0.63%)	⬇️
... and 14 more

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[lollipopjin]

LGTM