Lower sl_ahead in do-ra config to reduce RA timeout risk

ci-scripts/conf_files/gnb.band78.106prb.rfsim.phytest-dora.conf

@@ -195,6 +195,7 @@ RUs = (
          max_pdschReferenceSignalPower = -27;
          max_rxgain                    = 50;
          eNB_instances  = [0];
+         sl_ahead = 3;
          sdr_addrs = "addr=192.168.10.2,second_addr=192.168.20.2";
     }
 );