fix warnings

Author: Brian Chen

firebase-firestore/src/test/java/com/google/firebase/firestore/remote/RemoteSerializerTest.java

@@ -681,7 +681,6 @@ public void testNotEqualSerialization() {
     assertEquals(expectedFilter, apiFilter);
     FieldFilter roundTripped = serializer.decodeFieldFilter(apiFilter.getFieldFilter());
     assertEquals(roundTripped, inputFilter);
-    assertTrue(roundTripped instanceof FieldFilter);
   }
 
   @Test
@@ -795,7 +794,7 @@ private void unaryFilterTest(
                             .setOp(unaryOperator)));
 
     // Add extra ORDER_BY field for '!=' since it is an inequality.
-    if (op == "!=") {
+    if (op.equals("!=")) {
       structuredQueryBuilder.addOrderBy(
           Order.newBuilder()
               .setDirection(Direction.ASCENDING)