Increase prepared statement caching timeout further

Author: dkropachev

integration-tests/src/test/java/com/datastax/oss/driver/core/cql/PreparedStatementCachingIT.java

@@ -272,7 +272,7 @@ private void invalidationTestInner(
       // Isolated Cassandra and Scylla runners can lag long enough in CI that the removal callback
       // arrives late.
       await()
-          .atMost(15, TimeUnit.MINUTES)
+          .atMost(18, TimeUnit.MINUTES)
           .untilAsserted(
               () -> {
                 assertThat(removedQueryIds.get()).isNotEmpty().get().isEqualTo(queryId2);