Remove redundant force merge in rest tests

[finnegancarroll]

Description

Several aggregation rest tests assert on the number of optimized segments.
- match: { profile.shards.0.aggregations.0.debug.optimized_segments: 1 }

For these tests to be consistent our index can only have a single segment. As such we configure out test indices with 1 shard and no refresh interval to ensure a single segment.

settings:
  number_of_shards: 1
  number_of_replicas: 0
  refresh_interval: -1

We also force merge in these cases:

- do:
    indices.forcemerge:
      index: <index>
      max_num_segments: 1

These two operations are redundant so this pr removes the force merge step for these cases.

Related Issues

Inciting comment

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

✅ Gradle check result for 7fa1d93: SUCCESS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.01%. Comparing base (8ddb3ee) to head (7fa1d93).
Report is 48 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #16144      +/-   ##
============================================
+ Coverage     71.86%   72.01%   +0.15%     
- Complexity    64447    64492      +45     
============================================
  Files          5288     5288              
  Lines        301438   301439       +1     
  Branches      43552    43552              
============================================
+ Hits         216628   217087     +459     
+ Misses        67034    66489     -545     
- Partials      17776    17863      +87     

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[finnegancarroll]

@jainankitk can you take a look? Per conversation here: #16083 (comment)

[jainankitk]

@jainankitk can you take a look? Per conversation here: #16083 (comment)

Thanks @finnegancarroll for following up the discussion with this PR!