Don't hard require ext-redis to run the tests

Author: GrahamCampbell

composer.json

@@ -16,7 +16,6 @@
         "illuminate/redis": "^5.5 || ^6.0 || ^7.0 || ^8.0"
     },
     "require-dev": {
-        "ext-redis": "*",
         "graham-campbell/analyzer": "^2.4 || ^3.0",
         "graham-campbell/testbench": "^5.5",
         "phpunit/phpunit": "^6.5 || ^7.5 || ^8.4 || ^9.0",