feature-better-DE-scrollbar (prod)

[cgettings]

making scrollbar styling a little bit better but not on Firefox =(

PR checklist:

• [x] Changes previewed and QC'ed
• [ ] In PR, mention team member for FYI, review, or approval

New content (if applicable):

• [ ] Date updated
• [ ] Tags and keywords updated
• [ ] Feature box updated

New data (if applicable)

• [ ] Added to Recently Updated
• [ ] Added to 311-crosswalk