checkpoint: Fix checkpoint ack condition

[Raneet10]

Description

This PR fixes condition for checkpoint-ack transaction in post-handler.

Changes

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Changes only for a subset of nodes

Checklist

• I have added at least 2 reviewer or the whole pos-v1 team
• I have added sufficient documentation in code
• I will be resolving comments - if any - by pushing each fix in a separate commit and linking the commit hash in the comment reply

Testing

• I have added unit tests
• I have added tests to CI
• I have tested this code manually on local environment
• I have tested this code manually on remote devnet using express-cli
• I have tested this code manually on mumbai
• I have created new e2e tests into express-cli

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.13% 🎉

Comparison is base (1056c1d) 76.45% compared to head (116f11f) 76.58%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1043      +/-   ##
===========================================
+ Coverage    76.45%   76.58%   +0.13%     
===========================================
  Files           53       53              
  Lines         5911     5919       +8     
===========================================
+ Hits          4519     4533      +14     
+ Misses        1133     1128       -5     
+ Partials       259      258       -1     

Files Changed	Coverage Δ
checkpoint/side_handler.go	73.35% <100.00%> (+2.19%)	⬆️

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