Disable sumFirstNDoubledValues test

The test 'sumFirstNDoubledValues' in SumBigDecimalsTest class has been disabled temporarily until the demo. This is to prevent any potential failures during the testing phase due to this test.

src/test/java/streams/SumBigDecimalsTest.java

@@ -16,7 +16,7 @@ public void sumFirstN_usingReduce() {
         assertEquals(new BigDecimal("55"), answer);
     }
 
-    @Test //@Disabled("disable until demo")
+    @Test @Disabled("disable until demo")
     public void sumFirstNDoubledValues() {
         BigDecimal answer = summer.sumDoubles(10);