[Maintenance] Fixes XContentMapValues.filter call due to recent change in core

[DarshitChanpura]

Recent change in core: opensearch-project/OpenSearch#19976 broke the CI.

This change fixes it.

Check List

• New functionality includes testing
• New functionality has been documented
• New Roles/Permissions have a corresponding security dashboards plugin PR
• API changes companion pull request created
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
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[cwperks]

Thank you for the quick fix!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.46%. Comparing base (f4e573f) to head (84a5951).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5800      +/-   ##
==========================================
+ Coverage   73.37%   73.46%   +0.09%     
==========================================
  Files         434      437       +3     
  Lines       26618    26716      +98     
  Branches     3963     3954       -9     
==========================================
+ Hits        19530    19626      +96     
- Misses       5199     5207       +8     
+ Partials     1889     1883       -6     

Files with missing lines	Coverage Δ
...nsearch/security/compliance/FieldReadCallback.java	54.54% <100.00%> (ø)

... and 16 files with indirect coverage changes

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