ci: Use only the latest 'valac' for building

.travis.yml

@@ -9,14 +9,10 @@ cache:
 compiler:
     - gcc
 
-env:
-    - VALAC=valac-0.30
-    - VALAC=valac VALAFLAGS=--fatal-warnings
-
 before_install:
     - sudo add-apt-repository --yes ppa:vala-team
     - sudo apt-get update --quiet
-    - sudo apt-get install --yes --force-yes ${VALAC} libglib2.0-bin
+    - sudo apt-get install --yes --force-yes valac libglib2.0-bin
       libglib2.0-dev libsoup2.4-dev libsystemd-journal-dev libfcgi-dev
       python3-pip gcovr libgee-0.8-dev libctpl-dev libjson-glib-dev
       libmemcached-dev libmarkdown2-dev liblua5.2-dev valgrind