Css: Don’t cache support.reliableMarginRight; thanks @jdalton, @timmywil

Fixes #14731
Css: Fix the reliableMarginRight test in oldIE.

This fixes an error introduced by the previous commit.
Build: Upgrade npm devDependencies

(cherry-picked from d63243d085c797e53a965620c439277284eada59)
Build: Remove obsolete UglifyJS workaround

(cherry-picked from d41fc68d9b89d39f8c71ae9f810b72798ff3e9ac)