Fixed `composer lint` command invocation in `.travis-ci.yml`

.travis.yml

@@ -30,7 +30,7 @@ before_install:
 install:
   - if [[ $SETUP = 'stable' ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-stable --no-suggest; fi
   - if [[ $SETUP = 'lowest' ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-lowest --prefer-stable --no-suggest; fi
-  - if [[ $SETUP = 'lint' ]]; then travis_retry composer lint; fi
+  - if [[ $SETUP = 'lint' ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-stable --no-suggest; travis_retry composer lint; fi
 
 script:
   - vendor/bin/phpunit