remove build QGIS image at each commit

let it for cron jobs

.travis.yml

@@ -12,7 +12,7 @@ matrix:
         - DOCKER_DEPS_PUSH=$( [[ $TRAVIS_REPO_SLUG =~ qgis/QGIS ]] && [[ $TRAVIS_PULL_REQUEST =~ false ]] && echo "true" || echo "false" )
         - DOCKER_DEPS_IMAGE_REBUILD=$( [[ $TRAVIS_COMMIT_MESSAGE =~ '[docker] update dependencies' ]] && echo "true" || echo "false" )
         # on cron job, QGIS image is built and push without testing
-        - DOCKER_QGIS_IMAGE_BUILD_PUSH=$( [[ $TRAVIS_REPO_SLUG =~ qgis/QGIS ]] && [[ $TRAVIS_EVENT_TYPE =~ cron ]] && echo "true" || echo "true" ) # TODO: else false
+        - DOCKER_QGIS_IMAGE_BUILD_PUSH=$( [[ $TRAVIS_REPO_SLUG =~ qgis/QGIS ]] && [[ $TRAVIS_EVENT_TYPE =~ cron ]] && echo "true" || echo "false" )
         - QGIS_LAST_BUILD_SUCCESS=true # TODO use API to know if last build succeed https://developer.travis-ci.com/resource/builds
         - CCACHE_DIR=${HOME}/.ccache
       dist: trusty