Set UE RX to TX time to 4

0d0e1111 set to UE RX to TX time to 2 as
it was deemed that the UE could sustain this time. However, we noticed a
degradation of performance, so reset the RX to TX time to something
higher to ensure proper performance.

There is no need to restore the asserts, because while the performance
with 2 is not as good as 4, the UE can in principle handle this time.

openair1/PHY/impl_defs_top.h

@@ -272,7 +272,7 @@
 /* - between reception of pdsch and tarnsmission of its acknowlegment    */
 /* - between reception of un uplink grant and its related transmission   */
 // should be 2 as per NR standard, but current UE is not able to perform this value
-#define NR_UE_CAPABILITY_SLOT_RX_TO_TX           (2)
+#define NR_UE_CAPABILITY_SLOT_RX_TO_TX           (4)
 
 #define DURATION_RX_TO_TX (NR_UE_CAPABILITY_SLOT_RX_TO_TX)