Add IAM policy elasticloadbalancing:DescribeTargetHealth

[hanwen-pcluste]

This is necessary for pcluster describe-cluster to get healthy and unhealthy login nodes

References

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Checklist

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.14%. Comparing base (8641f35) to head (ffd4830).
Report is 17 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #6427      +/-   ##
===========================================
- Coverage    90.16%   90.14%   -0.03%     
===========================================
  Files          181      181              
  Lines        16059    16074      +15     
===========================================
+ Hits         14480    14490      +10     
- Misses        1579     1584       +5     

Flag	Coverage Δ
unittests	90.14% <ø> (-0.03%)	⬇️

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