Tests: Fix flakey htlc test

[jasonpaulos]

Summary

Fix for flakey htlc test, which is comparing exact account balance. I believe sometimes rewards are applied, so it's off by a small amount. Fixed this by comparing to the minimum expected amount of algos.

Example of a failure: https://app.circleci.com/pipelines/github/algorand/go-algorand/18425/workflows/259ccdba-c6c1-4093-abd9-e0c59e22a0d3/jobs/272733

Test Plan

Existing tests should pass

[jannotti]

That's reasonable, but maybe better to have the account go non-participating instead?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.19%. Comparing base (8d228c0) to head (f3ab4c0).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6017      +/-   ##
==========================================
- Coverage   55.89%   55.19%   -0.71%     
==========================================
  Files         481      481              
  Lines       68357    68357              
==========================================
- Hits        38210    37728     -482     
- Misses      27551    28002     +451     
- Partials     2596     2627      +31     

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