Allow Laravel 6.17

Author: HighLiuk

composer.json

@@ -14,11 +14,11 @@
     "require": {
         "php": ">=7.3",
         "guzzlehttp/guzzle": "^6.3 || ^7.0",
-        "illuminate/notifications": "^5.7",
-        "illuminate/support": "^5.7"
+        "illuminate/notifications": "^6.17",
+        "illuminate/support": "^6.17"
     },
     "require-dev": {
-        "orchestra/testbench": "3.7.*",
+        "orchestra/testbench": "^4.0",
         "phpunit/phpunit": "^7.5"
     },
     "autoload": {
@@ -38,7 +38,7 @@
     "config": {
         "sort-packages": true
     },
-    "extra" : {
+    "extra": {
         "laravel": {
             "providers": [
                 "NotificationChannels\\GoogleChat\\GoogleChatServiceProvider"