Multiprovider: review comments incorporated

Signed-off-by: suvaidkhan <khansuvaid@yahoo.com>

src/main/java/dev/openfeature/sdk/multiprovider/MultiProvider.java

@@ -95,6 +95,7 @@ public class MultiProvider extends EventProvider {
         List<Future<Boolean>> results = initPool.invokeAll(tasks);
         for (Future<Boolean> result : results) {
             if (!result.get()) {
+                initPool.shutdown();
                 throw new GeneralError("init failed");
             }
         }

src/test/java/dev/openfeature/sdk/multiProvider/MultiProviderTest.java

@@ -41,7 +41,6 @@ class MultiProviderTest extends BaseStrategyTest {
         MultiProvider multiProvider = new MultiProvider(providers, strategy);
         multiProvider.initialize(null);
 
-        assertNotNull(multiProvider);
         MultiProviderMetadata metadata = (MultiProviderMetadata) multiProvider.getMetadata();
         Map<String, Metadata> map = metadata.getOriginalMetadata();
         assertEquals(mockMetaData1, map.get(mockProvider1.getMetadata().getName()));