install-chromedriver.sh should not use apk to install chromedriver

[simonsdave]

would like to install a specific version of chromedriver from the downloads section of http://chromedriver.chromium.org/downloads

this works on Ubuntu but not for Alpine because the downloads @ http://chromedriver.chromium.org/downloads are Alpine compatible and so chromedriver is installed by install-chromedriver.sh using apk add chromium-chromedriver which provides no control over the version that's installed.

need control over the version of chromedriver that's installed.