setup: minimum Python is 3.8

This has been true for a while.

Signed-off-by: William Woodruff <william@trailofbits.com>

setup/setup.bash

@@ -35,15 +35,15 @@ if [[ "${0}" == "${BASH_SOURCE[0]}" ]]; then
  die "Internal error: setup harness was executed instead of being sourced?"
 fi
 
-# Check the Python version, making sure it's new enough (3.7+)
+# Check the Python version, making sure it's new enough (3.8+)
 # The installation step immediately below will technically catch this,
 # but doing it explicitly gives us the opportunity to produce a better
 # error message.
 vers=$(python -V | cut -d ' ' -f2)
 maj_vers=$(cut -d '.' -f1 <<< "${vers}")
 min_vers=$(cut -d '.' -f2 <<< "${vers}")
 
-[[ "${maj_vers}" == "3" && "${min_vers}" -ge 7 ]] || die "Bad Python version: ${vers}"
+[[ "${maj_vers}" == "3" && "${min_vers}" -ge 8 ]] || die "Bad Python version: ${vers}"
 
 # If the user didn't explicitly configure a Python version with
 # `actions/setup-python`, then we might be using the distribution's Python and