Remove coveralls integration

Author: chadicus

.coveralls.yml

@@ -40,7 +40,6 @@
     },
     "require-dev": {
         "helmich/mongomock": "^2.1",
-        "php-coveralls/php-coveralls": "^2.1",
         "phpunit/phpunit": "^6.5.2",
         "squizlabs/php_codesniffer": "^3.2",
         "subjective-php/psr-cache-mongodb": "^2.1"