removed env var

Author: daniel-sanche

.kokoro/presubmit/presubmit.cfg

@@ -5,9 +5,3 @@ env_vars: {
     key: "RUN_SYSTEM_TESTS"
     value: "false"
 }
-
-# TODO: remove explicit session setting after deprecating 3.7 and 3.8
-env_vars: {
-    key: "NOX_SESSION"
-    value: "unit-3.9 unit-3.10 unit-3.11 unit-3.12 unit-3.13 unit-3.14 docs lint lint_setup_py blacken cover"
-}