chore: Use server.close()

Author: jonathanedey

src/test/java/com/google/firebase/internal/ApacheHttp2TransportIT.java

@@ -316,7 +316,7 @@ public int getPort() {
 
     @Override
     public void close() {
-      server.initiateShutdown();
+      server.close();
     }
   }
 }