Increase Aerial-based L2 test core number

Testing has revealed that if PDCP drops some packets, the scheduler
falls behind with handling Slot.indication. It could be that we don't
have enough cores, which was reduced previously (from total 8 -> 2).
Reincrease to four cores to have a bit more headroom.

See-also: a18a4888ec ("Change number of cores used for OAI gNB from 8 to 2")

ci-scripts/yaml_files/sa_gnb_aerial/docker-compose.yaml

@@ -33,7 +33,7 @@ services:
       timeout: 5s
       retries: 5
   oai-gnb-aerial:
-    cpuset: "13-14"
+    cpuset: "13-16"
     image: ${REGISTRY-oaisoftwarealliance/}${GNB_IMG:-oai-gnb-aerial}:${TAG:-develop}
     depends_on:
       nv-cubb:

doc/Aerial_FAPI_Split_Tutorial.md

@@ -82,7 +82,7 @@ of the FAPI 10.04 version of the SRS PDU, and RX_Beamforming PDU.
 | Applicative Threads    | Allocated CPUs |
 |------------------------|----------------|
 | PTP & PHC2SYS Services | 41             |
-| OAI `nr-softmodem`     | 13-14          |
+| OAI `nr-softmodem`     | 13-16          |
 
 ## PTP configuration