Minor update to Lab 1a coversheet ("Pre-flight Checklist")

A new version of Lab 1a has been posted with revisions to the "Prep: What do you need to start?" section that add instructions for browser security settings.

Details:

Some newer browser versions have tightened security setting defaults that interfere with some Salesforce functions as noted in the Browser Security Settings Advisory posted here on 9/22. Adding these instructions to the 1a cover sheet ("Pre-flight Checklsit) should help prevent these issues from snagging students but please continue to urge them to read the Pre-flight Checklists before every lab and in particular, highlight this browser security setting issue to them at the beginning. Thanks!