Disable CI

The CI runner is pretty slow to set up (takes about 6 minutes to get
through the system dependencies needed to build GTK), and does not work
with dependencies as subprojects.

Until we figure out how to make it work, and make it work a bit faster,
we should drop CI and rely on Continuous for a while longer.

We can revert this commit as soon as we find out how to make things
work.

.gitlab-ci.yml

@@ -1,26 +0,0 @@
-image: fedora:27
-
-stages:
-  - build
-
-before_script:
-  - dnf install -y gcc meson gettext itstool redhat-rpm-config git
-                   glib2-devel
-                   gobject-introspection-devel
-                   json-glib-devel cups-devel colord-devel
-                   libxkbcommon-devel
-                   libXrender-devel libXcomposite-devel libXcursor-devel
-                   libXfixes-devel libXcursor-devel libXi-devel
-                   libXdamage-devel libXinerama-devel libXrandr-devel
-                   libepoxy-devel at-spi2-atk-devel avahi-gobject-devel
-                   cairo-devel cairo-gobject-devel atk-devel
-                   wayland-devel wayland-protocols-devel
-                   mesa-libEGL-devel mesa-libwayland-egl-devel
-                   vulkan-devel
-
-build:
-  stage: build
-  script:
-    - meson -Denable-x11-backend=true -Denable-wayland-backend=true -Denable-broadway-backend=true -Denable-vulkan=yes _build_full
-    - cd _build_full
-    - ninja