chore: remove phpdocumentor/reflection when no snippets exist (#5279)

Author: bshaffer

composer.json

@@ -27,8 +27,7 @@
  },
  "require-dev": {
  "phpunit/phpunit": "^4.8|^5.0|^8.0",
- "yoast/phpunit-polyfills": "^1.0",
- "phpdocumentor/reflection": "^3.0"
+ "yoast/phpunit-polyfills": "^1.0"
  },
  "suggest": {
  "ext-grpc": "Enables use of gRPC, a universal high-performance RPC framework created by Google.",