Fix block rewards endpoint

[Jayashsatolia403]

Fixes

Changes

Need to be mentioned in CHANGELOG.md?

Tests

Tasks to complete before merging PR:

• Ensure system tests are passing. If not Run them manually to check for any regressions 📋
• Do any new system tests need added to test this change? do any existing system tests need updated? If so create a PR at 0chain/system_test
• Merge your system tests PR to master AFTER merging this PR

Associated PRs (Link as appropriate):

• blobber:
• gosdk:
• system_test:
• zboxcli:
• zwalletcli:
• Other: ...

[codecov-commenter]

Codecov Report

Merging #2574 (97bb840) into sprint-july-1 (d583b0b) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

❗ Current head 97bb840 differs from pull request most recent head d9ea957. Consider uploading reports for the commit d9ea957 to get more accurate results

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@@                Coverage Diff                @@
##           sprint-july-1    #2574      +/-   ##
=================================================
- Coverage          28.79%   28.79%   -0.01%     
=================================================
  Files                380      380              
  Lines              64101    64091      -10     
=================================================
- Hits               18461    18458       -3     
+ Misses             43460    43454       -6     
+ Partials            2180     2179       -1     

Flag	Coverage Δ
Unit-Tests	28.79% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...go/0chain.net/smartcontract/dbs/event/challenge.go	28.88% <0.00%> (-4.88%)	⬇️
...net/smartcontract/dbs/event/reward_provider_dev.go	0.00% <0.00%> (ø)
...o/0chain.net/smartcontract/storagesc/allocation.go	50.99% <0.00%> (-0.17%)	⬇️

... and 6 files with indirect coverage changes

[dabasov]

lgtm