Tidy up the code and comments in DeleteCollection.java

Author: djsauble

astra-db-client/src/test/java/com/dtsx/astra/sdk/documentation/DeleteCollection.java

@@ -4,11 +4,9 @@
 
 public class DeleteCollection {
   public static void main(String[] args) {
-
-    // Given an active db
     AstraDB db = new AstraDB("<token>", "<api_endpoint>");
 
-    // Find a collection
+    // Delete an existing collection
     db.deleteCollection("collection_vector2");
   }
 }