Trying to enable Travis PHP 7.3 again

Author: moufmouf

.travis.yml

@@ -1,6 +1,6 @@
 language: php
 php:
- #- 7.3
+ - 7.3
  - 7.4
 before_script:
 - composer self-update --2

composer.json

@@ -23,7 +23,7 @@
         "phpunit/phpunit": "^8.5.8",
         "squizlabs/php_codesniffer": "^2.9.2",
         "couscous/couscous": "^1.8",
-        "infection/infection": "^0.18.2"
+        "infection/infection": "^0.17.7 || ^1.18.2"
     },
     "autoload": {
         "psr-4": {