NR RRC/SDAP: enable SDAP by default and update CI/docs

- Change gNB RRC enable_sdap default to true
- Update RRC and RUNMODEM docs to reflect new default behavior
- Clean up CI gNB configs by removing redundant enable_sdap=1
- Keep explicit SDAP disable config for NFAPI gNB VNF

ci-scripts/conf_files/gnb.sa.band66.106prb.rfsim.conf

@@ -18,7 +18,7 @@ gNBs =
     ////////// Physical parameters:
 
     min_rxtxtime                                              = 6;
-    enable_sdap = 1;
+    enable_sdap = 0;
 
     servingCellConfigCommon = (
     {

ci-scripts/conf_files/untested/gnb.sa.band66.fr1.106PRB.usrpn300.conf

@@ -18,7 +18,7 @@ gNBs =
     ////////// Physical parameters:
 
     min_rxtxtime                                              = 6;
-    enable_sdap = 1;
+    enable_sdap = 0;
 
     servingCellConfigCommon = (
     {