tests: Simplify logic in Elasticsearch integration tests for skipping non-async methods

[nr-ahemsath]

Simplify the logic in the Elasticsearch integration tests which skips testing non-async methods in the latest versions of Elastic.Clients.Elasticsearch.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.86%. Comparing base (7a86f61) to head (e1cb078).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2574      +/-   ##
==========================================
- Coverage   80.87%   80.86%   -0.02%     
==========================================
  Files         458      458              
  Lines       28985    28985              
  Branches     3184     3184              
==========================================
- Hits        23441    23438       -3     
- Misses       4755     4757       +2     
- Partials      789      790       +1     

Flag	Coverage Δ
Agent	81.78% <ø> (-0.02%)	⬇️
Profiler	72.59% <ø> (ø)

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see 2 files with indirect coverage changes