build: Remove install command samples

test/README.md contains comprehensive install instructions.

Author: hebasto

test/lint/lint-python.sh

@@ -82,10 +82,10 @@ enabled=(
 )
 
 if ! command -v flake8 > /dev/null; then
-    echo "Skipping Python linting since flake8 is not installed. Install by running \"pip3 install flake8\""
+    echo "Skipping Python linting since flake8 is not installed."
     exit 0
 elif PYTHONWARNINGS="ignore" flake8 --version | grep -q "Python 2"; then
-    echo "Skipping Python linting since flake8 is running under Python 2. Install the Python 3 version of flake8 by running \"pip3 install flake8\""
+    echo "Skipping Python linting since flake8 is running under Python 2. Install the Python 3 version of flake8."
     exit 0
 fi