travis: changed PhpStan level to 5

Author: dg

.travis.yml

@@ -41,7 +41,7 @@ jobs:
                 - travis_retry composer install --no-progress --prefer-dist
 
             script:
-                - php temp/phpstan/phpstan.phar analyse --autoload-file vendor/autoload.php --level 7 --configuration tests/phpstan.neon src
+                - php temp/phpstan/phpstan.phar analyse --autoload-file vendor/autoload.php --level 5 --configuration tests/phpstan.neon src
 
 
         -   stage: Code Coverage