travis: drop debootstrap workaround

Move to qubes-builder

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

.travis.yml

@@ -2,8 +2,6 @@ sudo: required
 dist: trusty
 language: generic
 install: git clone https://github.com/QubesOS/qubes-builder ~/qubes-builder
-# debootstrap in trusty is old...
-before_script: sudo ln -s sid /usr/share/debootstrap/scripts/stretch
 script: ~/qubes-builder/scripts/travis-build
 env:
  - DISTS_VM=fc23 USE_QUBES_REPO_VERSION=3.2 USE_QUBES_REPO_TESTING=1