Disable chrome screenshotter tests until we can determine why it's producing different results.

Test Plan:
- run `make screenshots` and verify that it doesn't start the chrome docker image

Auditors: alpert, emily

dockers/Screenshotter/screenshotter.sh

@@ -8,7 +8,7 @@
 # directly.
 
 status=0
-for browserTag in firefox:2.46.0 chrome:2.46.0; do
+for browserTag in firefox:2.46.0; do
     browser=${browserTag%:*}
     image=selenium/standalone-${browserTag}
     echo "Starting container for ${image}"