demo/browser/index.html: Remove unused file
demo/browser/index.html: Remove unused file

It no longer works because simplebar.umd.js was renamed to
simplebar.js, and was replaced with demo/examples.html a while ago.

Signed-off-by: Anders Kaseorg <087231934ba8fcf78bc142ce37d193b895ac03c4@mit.edu>

Grsmto/simplebar,Grsmto/simplebar,Grsmto/simplebar