It has a lot of files because that's the point

Removes ce to ee differences for snowplow file

It takes a lot of lines to move a script

pdf.js is available on npm. Importing the dependency from there instead
of vendoring it has certain benefits, e.g. the discoverability of
updates (especially security fixes).

Fix PDF.js vulnerability

See merge request gitlab/gitlabhq!2999

Remove references to the vendored copies of At.js and jquery.carat
as well as the legacy rails wrapper gem.