remove unused files

doc/config.json

···
-{
-  "database": {
-    "host": "localhost",
-    "port": 5432,
-    "credentials": {
-      "username": "admin",
-      "password": "secret"
-    }
-  },
-  "features": ["auth", "logging", "metrics"]
-}

doc/rfc6901_example.json

···
-{
-  "foo": ["bar", "baz"],
-  "": 0,
-  "a/b": 1,
-  "c%d": 2,
-  "e^f": 3,
-  "g|h": 4,
-  "i\\j": 5,
-  "k\"l": 6,
-  " ": 7,
-  "m~n": 8
-}