fix: [2.4] Remove frequently updating metric to avoid mutex contention

[bigsheeper]

issue: #37630

Reduce the frequency of updateIndexTasksMetrics to avoid holding the mutex for long periods.

pr: #38775

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.42%. Comparing base (995d5e1) to head (96fb8fd).
Report is 1 commits behind head on 2.4.

❗ Current head 96fb8fd differs from pull request most recent head d2d11d9

Please upload reports for the commit d2d11d9 to get more accurate results.

Additional details and impacted files

@@             Coverage Diff             @@
##              2.4   #38776       +/-   ##
===========================================
- Coverage   80.44%   70.42%   -10.02%     
===========================================
  Files        1079     1079               
  Lines      169909   169906        -3     
===========================================
- Hits       136678   119653    -17025     
- Misses      28730    45749    +17019     
- Partials     4501     4504        +3     

Files with missing lines	Coverage Δ
internal/datacoord/index_meta.go	97.62% <100.00%> (+1.63%)	⬆️
internal/querycoordv2/task/scheduler.go	90.05% <100.00%> (+0.72%)	⬆️

... and 270 files with indirect coverage changes

[mergify]

@bigsheeper E2e jenkins job failed, comment /run-cpu-e2e can trigger the job again.

[mergify]

@bigsheeper E2e jenkins job failed, comment /run-cpu-e2e can trigger the job again.

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: bigsheeper
To complete the pull request process, please ask for approval from liliu-z after the PR has been reviewed.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• internal/datacoord/OWNERS
• internal/querycoordv2/task/OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[mergify]

@bigsheeper E2e jenkins job failed, comment /run-cpu-e2e can trigger the job again.