Remove redundant -GN bot suffixes.

The GN in the name only matters for iOS bots now.  All the others are GN-only.

This revealed a couple redundant build bots: we had two each of Win x86_64 Debug and Release builders, one with -GN and one not.

I have intentionally not resorted gen_tasks.go to keep the diff looking somewhat sane.  I'd be happy to sort here or to follow up with a re-sort CL.

Change-Id: I2f8a136a1fbde416739966e27685b52b94b50cf6
Reviewed-on: https://skia-review.googlesource.com/5545
Reviewed-by: Eric Boren <borenet@google.com>
tree: e8604bbe4f17137f2d314043625d90e42c5d7323
  1. recipe_modules/
  2. recipes.py
  3. recipes/