Exclude 'benchmarks' from codecov report

[ketanv3]

Description

Updated codecov.yml to exclude the "benchmarks" directory from the code coverage report.

Check List

• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/20615/
• CommitID: b296e97
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/20614/
• CommitID: 57363dd
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/20616/
• CommitID: 825fb9f

[codecov]

Codecov Report

Merging #8805 (825fb9f) into main (6cc8da5) will increase coverage by 0.45%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main    #8805      +/-   ##
============================================
+ Coverage     70.61%   71.06%   +0.45%     
- Complexity    56909    57199     +290     
============================================
  Files          4771     4757      -14     
  Lines        270253   269789     -464     
  Branches      39502    39450      -52     
============================================
+ Hits         190837   191736     +899     
+ Misses        63250    61889    -1361     
+ Partials      16166    16164       -2     

see 535 files with indirect coverage changes