[Gameplay] Varus W base damage doesn't scale.

Varus' Blight detonation damage is not scaling with abilities rank. The base damage is locked at 2.5% max hp per blight stack, when it should scale from 3% to 5% max hp. This is a pretty significant amount of damage that is missing from Varus' combo.

The bug is easily demonstrated in the practice tool using target dummies:

1. Add an enemy target dummy.
2. Attack the dummy once with at least one (but less than 5) ranks in W.
3. Pop the applied blight stack with W, Q, or R.
4. Add one or more ranks to W.
5. Repeat steps 2-3 and observe that the blight pop damage is unchanged.