ci: Upgrade EEST to v4.2.0 develop

[chfast]

This upgrades EEST to v4.2.0. It also only runs develop fixtures because they include the stable ones.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.27%. Comparing base (4d6d30e) to head (7dd30a1).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1191      +/-   ##
==========================================
- Coverage   94.91%   94.27%   -0.65%     
==========================================
  Files         171      171              
  Lines       19675    19675              
==========================================
- Hits        18675    18548     -127     
- Misses       1000     1127     +127     

Flag	Coverage Δ
eof_execution_spec_tests	2.53% <ø> (ø)
ethereum_tests	22.36% <ø> (ø)
ethereum_tests_silkpre	17.87% <ø> (ø)
execution_spec_tests	?
unittests	92.46% <ø> (ø)

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see 12 files with indirect coverage changes

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