Increase limit on number of open challenges per fetching

[Jayashsatolia403]

Changes

Fixes

Tests

Tasks to complete before merging PR:

• [ ] Ensure system tests are passing. If not Run them manually to check for any regressions :clipboard:
• [ ] 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):

• 0chain:
• gosdk:
• system_test:
• zboxcli:
• zwalletcli:
• Other: ...

[codecov-commenter]

Codecov Report

Merging #1249 (037c16a) into sprint-1.11 (848591c) will not change coverage. The diff coverage is n/a.

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@@             Coverage Diff              @@
##           sprint-1.11    #1249   +/-   ##
============================================
  Coverage        25.54%   25.54%           
============================================
  Files               84       84           
  Lines             9385     9385           
============================================
  Hits              2397     2397           
  Misses            6691     6691           
  Partials           297      297           

Flag	Coverage Δ
Unit-Tests	25.54% <ø> (ø)

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