[ci] Remove sphinx directory (from other builds?)

.gitlab-ci.yml

@@ -24,3 +24,4 @@ browser_test:
     - apt-get install -y locales > /dev/null
     - echo "en_US UTF-8" > /etc/locale.gen
     - locale-gen en_US.UTF-8
+    - rm -rf ${CI_PROJECT_DIR}/sphinx