updated travis config: removed COMPOSER_FLAGS env

Author: vimishor

.travis.yml

@@ -13,7 +13,7 @@ matrix:
 
 before_script:
   - travis_retry composer self-update
-  - travis_retry composer install ${COMPOSER_FLAGS} --no-interaction --prefer-source
+  - travis_retry composer install --no-interaction --prefer-source
 
 script:
   - mkdir -p ./build/logs