Update .gitlab-ci.yml

.gitlab-ci.yml

 image: ruby:2.3
 
 before_script:
-  - apt-get update -qq && apt-get install -y -qq libbluetooth-dev cmake valgrind qmake-qt5
+  - apt-get update -qq && apt-get install -y -qq libbluetooth-dev cmake valgrind qt5-default
 
 stages:
   - build