[Backport 2.x] Updated MAINTAINERS.md format.

[opensearch-trigger-bot]

Backport f4ab469 from #1224

[codecov-commenter]

Codecov Report

Merging #1233 (c02c5bc) into 2.x (de79815) will decrease coverage by 35.55%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##                2.x    #1233       +/-   ##
=============================================
- Coverage     98.32%   62.76%   -35.56%     
=============================================
  Files           346       10      -336     
  Lines          8768      658     -8110     
  Branches        554      119      -435     
=============================================
- Hits           8621      413     -8208     
- Misses          142      192       +50     
- Partials          5       53       +48     

Flag	Coverage Δ
query-workbench	62.76% <ø> (?)
sql-engine	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...org/opensearch/sql/analysis/HighlightAnalyzer.java
...l/opensearch/data/utils/OpenSearchJsonContent.java
...org/opensearch/sql/expression/env/Environment.java
...rotocol/response/format/JsonResponseFormatter.java
...ql/prometheus/storage/PrometheusStorageEngine.java
...rage/querybuilder/SeriesSelectionQueryBuilder.java
...ensearch/storage/system/OpenSearchSystemIndex.java
...arch/storage/system/OpenSearchSystemIndexScan.java
.../lucene/relevance/FunctionParameterRepository.java
...nsearch/sql/planner/physical/RareTopNOperator.java
... and 346 more

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