Should not require the ignore platform reqs now we add ext-mongo to composer

Author: redthor

.travis.yml

@@ -22,7 +22,7 @@ before_script:
   - composer config "platform.ext-mongo" "1.6.16"
   - composer self-update
   # To be removed when this issue is resolved: https://github.com/composer/composer/issues/5355
-  - if [[ "$COMPOSER_FLAGS" == *"--prefer-lowest"* ]]; then composer update --prefer-dist --no-interaction --prefer-stable --ignore-platform-reqs --quiet; fi
+  - if [[ "$COMPOSER_FLAGS" == *"--prefer-lowest"* ]]; then composer update --prefer-dist --no-interaction --prefer-stable --quiet; fi
   - composer update -v ${COMPOSER_FLAGS}
 
 script: