bump testing

Author: wilr

composer.json

@@ -19,7 +19,7 @@
     "level51/silverstripe-jwt-utils": "^1.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^5.7",
+    "phpunit/phpunit": "^9.5",
     "squizlabs/php_codesniffer": "^3"
   },
   "extra": {