update test-samples-impl.sh

Author: chalmerlowe

.kokoro/test-samples-impl.sh

@@ -33,7 +33,6 @@ export PYTHONUNBUFFERED=1
 env | grep KOKORO
 
 # Install nox
-# `virtualenv==20.26.6` is added for Python 3.7 compatibility
 python3.9 -m pip install --upgrade --quiet nox virtualenv==20.26.6
 
 # Use secrets acessor service account to get secrets