fix coordiantor assign task strategy

[georgehao]

Purpose or design rationale of this PR

Describe your change. Make sure to answer these three questions: What does this PR do? Why does it do it? How does it do it?

PR title

Your PR title must follow conventional commits (as we are doing squash merge for each PR), so it must start with one of the following types:

• build: Changes that affect the build system or external dependencies (example scopes: yarn, eslint, typescript)
• ci: Changes to our CI configuration files and scripts (example scopes: vercel, github, cypress)
• docs: Documentation-only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that doesn't fix a bug, or add a feature, or improves performance
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
• test: Adding missing tests or correcting existing tests

Deployment tag versioning

Has tag in common/version.go been updated or have you added bump-version label to this PR?

• No, this PR doesn't involve a new deployment, git tag, docker image tag
• Yes

Breaking change label

Does this PR have the breaking-change label?

• No, this PR is not a breaking change
• Yes

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 5.88235% with 16 lines in your changes missing coverage. Please review.

Project coverage is 52.01%. Comparing base (ec4dcd0) to head (d8793c6).

Files	Patch %	Lines
coordinator/cmd/api/app/mock_app.go	0.00%	16 Missing ⚠️

Additional details and impacted files

@@                                    Coverage Diff                                    @@
##           feat-coordinator-add-blob-bytes-in-batch-proving-task    #1495      +/-   ##
=========================================================================================
+ Coverage                                                  51.90%   52.01%   +0.11%     
=========================================================================================
  Files                                                        156      156              
  Lines                                                      12712    12684      -28     
=========================================================================================
  Hits                                                        6598     6598              
+ Misses                                                      5548     5520      -28     
  Partials                                                     566      566              

Flag	Coverage Δ
common	47.35% <ø> (ø)
coordinator	17.20% <5.88%> (+0.30%)	⬆️
database	42.85% <ø> (ø)
rollup	55.68% <ø> (ø)

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