Remove System.out.println. (#316)

Motivation:

Applications are improperly printing messages to the log, causing overload in certain situations. There is no need for a println since the log is already being managed by slf4j.

Modifications:

Remove println from buildAsync method

Result:

No improper messages are displayed in the log, and there is no more overload.

Co-authored-by: Danilo Rodrigues <danilo.rodrigues@accenture.com>

core/src/main/java/com/datastax/oss/driver/api/core/session/SessionBuilder.java

@@ -822,7 +822,6 @@ public SelfT withMetricRegistry(@Nullable Object metricRegistry) {
  */
  @NonNull
  public CompletionStage<SessionT> buildAsync() {
- System.out.println("Using Scylla optimized driver!!!");
  LOG.info("Using Scylla optimized driver!!!");
  CompletionStage<CqlSession> buildStage = buildDefaultSessionAsync();
  CompletionStage<SessionT> wrapStage = buildStage.thenApply(this::wrap);