test(aws-sdk): remove runs for Node.js <18.x

[trivikr]

Which problem is this PR solving?

• Support for Node.js <18.x as dropped in chore!: update to JS SDK 2.x #2738

Short description of the changes

• Remove runs for Node.js <18.x

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.51%. Comparing base (37d8ce1) to head (0c47546).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2763      +/-   ##
==========================================
+ Coverage   90.49%   90.51%   +0.01%     
==========================================
  Files         166      166              
  Lines        8020     8020              
  Branches     1533     1533              
==========================================
+ Hits         7258     7259       +1     
+ Misses        762      761       -1     

see 1 file with indirect coverage changes

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[pichlermarc]

overall looks good, please keep the skip-test-if.js script around though. we'll likely need it for other instrumentations soon.

[trivikr]

This change was done in #2700 (comment)