Tools: fix configparser version for python2

Tools/environment_install/install-prereqs-ubuntu.sh

@@ -139,7 +139,7 @@ fi
 BASE_PKGS="build-essential ccache g++ gawk git make wget"
 if [ ${RELEASE_CODENAME} == 'xenial' ] || [ ${RELEASE_CODENAME} == 'bionic' ]; then
     # use fixed version for package that drop python2 support
-    PYTHON_PKGS="future lxml pymavlink MAVProxy pexpect flake8==3.7.9 geocoder empy configparser==5.0.0 click==7.1.2 decorator==4.4.2"
+    PYTHON_PKGS="future lxml pymavlink MAVProxy pexpect flake8==3.7.9 geocoder empy configparser==4.0.2 click==7.1.2 decorator==4.4.2"
 else
     PYTHON_PKGS="future lxml pymavlink MAVProxy pexpect flake8 geocoder empy"
 fi