Update dependency net.dv8tion:JDA to v6

pom.xml

@@ -22,7 +22,7 @@
         <dependency>
             <groupId>net.dv8tion</groupId>
             <artifactId>JDA</artifactId>
-            <version>5.5.1</version>
+            <version>6.0.0-preview_DEV</version>
         </dependency>
         <!-- JDA depends on SLF4J for logging -->
         <dependency>
@@ -91,7 +91,7 @@
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter-api</artifactId>
-            <version>5.13.4</version>
+            <version>5.13.0</version>
             <scope>test</scope>
         </dependency>
     </dependencies>