fix: no env var manipulation in VerifyOPCM tests

[smartcontracts]

Description
Environment variables should not be directly manipulated in tests because they cause issues when different tests run in parallel that need those env vars to have specific values.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.12%. Comparing base (66e1ddc) to head (f34cd67).
⚠️ Report is 18 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #17813      +/-   ##
===========================================
+ Coverage    74.62%   81.12%   +6.50%     
===========================================
  Files          174      119      -55     
  Lines        11096     6311    -4785     
===========================================
- Hits          8280     5120    -3160     
+ Misses        2672     1191    -1481     
+ Partials       144        0     -144     

Flag	Coverage Δ
cannon-go-tests-64	?
contracts-bedrock-tests	81.12% <ø> (ø)

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see 55 files with indirect coverage changes

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