[ci] Move exporting of variables to "variables" section

.gitlab-ci.yml

@@ -14,6 +14,9 @@ browser_test:
   image: docker.idiap.ch/beat/ci.env.editor:0.0.1r0
   variables:
     BEAT_BROWSER_TESTS: "true"
+    LANG: "en_US.UTF-8"
+    LANGUAGE: "en_US:en"
+    LC_ALL: "en_US.UTF-8"
   dependencies:
     - build_linux_36
   before_script:
@@ -21,6 +24,3 @@ browser_test:
     - apt-get install -y locales > /dev/null
     - echo "en_US UTF-8" > /etc/locale.gen
     - locale-gen en_US.UTF-8
-    - export LANG=en_US.UTF-8
-    - export LANGUAGE=en_US:en
-    - export LC_ALL=en_US.UTF-8