[Backport 2.x] Remove concurrency based minimum file cache size restriction

[opensearch-trigger-bot]

Backport 3947cb4 from #8294.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.snapshots.RestoreSnapshotIT.testRestoreInSameRemoteStoreEnabledIndex

• URL: https://build.ci.opensearch.org/job/gradle-check/18758/
• CommitID: 676faa0
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

Merging #8367 (676faa0) into 2.x (b12a45a) will increase coverage by 0.05%.
The diff coverage is 73.07%.

@@             Coverage Diff              @@
##                2.x    #8367      +/-   ##
============================================
+ Coverage     70.62%   70.67%   +0.05%     
+ Complexity    56924    56915       -9     
============================================
  Files          4714     4714              
  Lines        269648   269657       +9     
  Branches      39857    39863       +6     
============================================
+ Hits         190434   190585     +151     
+ Misses        62857    62658     -199     
- Partials      16357    16414      +57     

Impacted Files	Coverage Δ
.../fieldcomparator/DoubleValuesComparatorSource.java	53.33% <0.00%> (-3.34%)	⬇️
...a/fieldcomparator/FloatValuesComparatorSource.java	42.85% <0.00%> (-3.58%)	⬇️
...ata/fieldcomparator/IntValuesComparatorSource.java	46.15% <0.00%> (-3.85%)	⬇️
...ta/fieldcomparator/LongValuesComparatorSource.java	50.00% <0.00%> (-2.95%)	⬇️
...comparator/UnsignedLongValuesComparatorSource.java	11.42% <0.00%> (ø)
...nsearch/index/fielddata/IndexNumericFieldData.java	86.20% <87.50%> (+0.49%)	⬆️
...org/opensearch/index/fielddata/IndexFieldData.java	75.47% <100.00%> (+1.47%)	⬆️
...index/store/remote/filecache/FileCacheFactory.java	92.30% <100.00%> (-1.45%)	⬇️

... and 475 files with indirect coverage changes