Update DeleteDatabase.java

* Use the standard two-space indent
* Reword the comment
* Simplify placeholders

Author: djsauble

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

@@ -3,10 +3,10 @@
 import com.dtsx.astra.sdk.AstraDBAdmin;
 
 public class DeleteDatabase {
-    public static void main(String[] args) {
-        AstraDBAdmin client = new AstraDBAdmin("<replace_with_token>");
+  public static void main(String[] args) {
+    AstraDBAdmin client = new AstraDBAdmin("<token>");
 
-        // Delete from its Name
-        client.deleteDatabase("<replace_with_db_name>");
-    }
+    // Delete an existing database
+    client.deleteDatabase("<database_name>");
+  }
 }