Remove deprecated test configuration for meetup exercise

The `tests.toml` file and specific keys in `config.json` for the meetup exercise have been removed. These changes clean up outdated metadata and streamline the exercise configuration.

Author: Jegors Cemisovs

exercises/concept/meetup/.meta/config.json

@@ -33,12 +33,6 @@
     "exemplar": [
       ".meta/src/reference/java/Meetup.java"
     ],
-    "example": [
-      ".meta/src/reference/java/Meetup.java"
-    ],
-    "editor": [
-      "src/main/java/MeetupSchedule.java"
-    ],
     "invalidator": [
       "build.gradle"
     ]