partial revert dash#4807: enable more multi-threading and caching in …

…linters

reverts:
- 3e6385e (only `lint-python.sh`)

test/lint/lint-python.sh

@@ -91,18 +91,10 @@ elif PYTHONWARNINGS="ignore" flake8 --version | grep -q "Python 2"; then
     exit 0
 fi
 
-FLAKECMD=flake8
-
-if command -v flake8-cached > /dev/null; then
-    FLAKECMD=flake8-cached
-else
-    echo "Consider install flake8-cached for cached flake8 results."
-fi
-
 EXIT_CODE=0
 
 # shellcheck disable=SC2046
-if ! PYTHONWARNINGS="ignore" $FLAKECMD --ignore=B,C,E,F,I,N,W --select=$(IFS=","; echo "${enabled[*]}") $(
+if ! PYTHONWARNINGS="ignore" flake8 --ignore=B,C,E,F,I,N,W --select=$(IFS=","; echo "${enabled[*]}") $(
     if [[ $# == 0 ]]; then
         git ls-files "*.py" | grep -vE "src/(immer)/"
     else