docs: Update CONTRIBUTING to reference soundness checks and remove advice to run locally #97
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Motivation
scripts/soundness.sh was deleted in #5 which moved CI to GitHub Actions.
resolves #96
Modifications
Remove the instruction to run
scripts/soundness.shfromCONTRIBUTING.md.Result
Documentation no longer refers to nonexistent scripts.
Test Plan
No functional change.