Apparently, the updated version of this has a serious scrolling
performance problem in the left sidebar that basically makes scrolling
in that area unusable.
This reverts commit b683b2d3c3.
- Remove `jquery-mousewheel` from `static/third` and fetch it from npm.
- Upgrade `jquery-mousewheel` to 3.1.6.
- Bump up the `PROVISION_VERSION` to 4.5.
- Change some js code to comply with this `jquery-mousewheel` version.
Part of #1709.