Optimize docker image

Dockerfile

@@ -1,16 +1,6 @@
 # https://github.com/joyzoursky/docker-python-chromedriver
 # https://github.com/TomRoush/python-selenium-firefox-docker
-# FROM tomroush/python-selenium-firefox-docker:latest
-FROM ubuntu:20.04
-
-ARG DEBIAN_FRONTEND=noninteractive
-RUN apt-get update && apt-get install -y \
-  python3 python3-pip \
-  firefox-geckodriver \
-  xvfb \
-  && rm -rf /var/lib/apt/lists/*
-
-RUN pip3 install --no-cache-dir selenium
+FROM tomroush/python-selenium-firefox-docker:latest
 
 ENV SELENIUM_HEADLESS=true