Remove Vector from the default LESS import path

When Ia193571a added Vector to core for VectorBeta's benefit it introduced
a regression that broke all skins that used imports like 'variables.less'
which happen to match a filename used by Vector.

These paths aren't supposed to be exposed anyway, and VectorBeta has been
fixed to no longer rely on this.

Bug: 64595
Change-Id: Iee47bdc23630e02ccfcbd28496ec5268892eb629
Merge "Remove Vector from the default LESS import path"