refactor(scyllaclient): reduce info to debug on closest DC

This log does not contain any useful information, but it clogs
the log files since checking for closest DC is done during
every fresh scyllaclient creation, which is done by the
config cache service every minute.

pkg/scyllaclient/client_ping.go

@@ -119,7 +119,7 @@ func (c *Client) CheckHostsConnectivity(ctx context.Context, hosts []string) []e
 // the lowest latency over 3 Ping() invocations across random selection of
 // hosts for each DC.
 func (c *Client) ClosestDC(ctx context.Context, dcs map[string][]string) ([]string, error) {
-	c.logger.Info(ctx, "Measuring datacenter latencies", "dcs", extractKeys(dcs))
+	c.logger.Debug(ctx, "Measuring datacenter latencies", "dcs", extractKeys(dcs))
 
 	if len(dcs) == 0 {
 		return nil, errors.Errorf("no dcs to choose from")