travis: Switch to autobuilt Docker images

Since Archlinux switched to PyQt 5.6, we can now use the autobuilt image
without a handbuilt PyQt. This means we have an up-to-date image with
each build again.

scripts/dev/ci/travis_run.sh

@@ -1,12 +1,8 @@
 #!/bin/bash
 
 if [[ $DOCKER ]]; then
-    # To build a fresh image:
-    # docker build -t img misc/docker/$DOCKER
-    # docker run --privileged -v $PWD:/outside img
-
     docker run --privileged -v $PWD:/outside \
-        thecompiler/qutebrowser-manual:$DOCKER
+        thecompiler/qutebrowser:$DOCKER
 else
     args=()
     [[ $TESTENV == docs ]] && args=('--no-authors')