Fix challenge numbers for expired allocations

[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 #2501 (9446a73) into staging (381429e) will increase coverage by 0.01%.
The diff coverage is 50.00%.

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@@             Coverage Diff             @@
##           staging    #2501      +/-   ##
===========================================
+ Coverage    28.81%   28.82%   +0.01%     
===========================================
  Files          380      380              
  Lines        63924    63935      +11     
===========================================
+ Hits         18420    18431      +11     
+ Misses       43332    43325       -7     
- Partials      2172     2179       +7     

Flag	Coverage Δ
Unit-Tests	28.82% <50.00%> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
...e/go/0chain.net/smartcontract/dbs/event/blobber.go	31.40% <0.00%> (-0.39%)	⬇️
...go/0chain.net/smartcontract/storagesc/challenge.go	28.72% <0.00%> (+0.15%)	⬆️
...o/0chain.net/smartcontract/storagesc/allocation.go	50.87% <75.00%> (+0.15%)	⬆️

... and 5 files with indirect coverage changes

[dabasov]

lgtm

[peterlimg]

LGTM