Issue #165 - Update Firefox to version 67.0

* Updated the Dockerfile

Author: ppodgorsek

Dockerfile

@@ -18,7 +18,7 @@ ENV ROBOT_THREADS 1
 # Dependency versions
 ENV CHROMIUM_VERSION 73.0.*
 ENV FAKER_VERSION 4.2.0
-ENV FIREFOX_VERSION 66.0*
+ENV FIREFOX_VERSION 67.0*
 ENV GECKO_DRIVER_VERSION v0.22.0
 ENV PABOT_VERSION 0.53
 ENV PYTHON_PIP_VERSION 18.0*