PCU_Tests: use real values for c_BssgpCell{Mcc,Mnc}

There is no such country/operator with MCC=023/MNC=43.  Wireshark
complains about that when looking at the BSSGP messahes:

  Mobile Country Code (MCC): Unknown (23)
  Mobile Network Code (MNC): Unknown (43)

This may look confusing, let's better use some real country/operator:

  Mobile Country Code (MCC): Central African Rep. (623)
  Mobile Network Code (MNC): Celca (Socatel) (03)

Change-Id: Idc22128657d10893aa5c6d8ec80538a764de5c42
Related: OS#5901
diff --git a/pcu/PCU_Tests.ttcn b/pcu/PCU_Tests.ttcn
index 6e858d5..15ea195 100644
--- a/pcu/PCU_Tests.ttcn
+++ b/pcu/PCU_Tests.ttcn
@@ -5132,8 +5132,8 @@
 	return dl_block;
 }
 
-private const GsmMcc c_BssgpCellMcc := '023'H;
-private const GsmMnc c_BssgpCellMnc := '43'H;
+private const GsmMcc c_BssgpCellMcc := '623'H;	/* MCC: Central African Republic */
+private const GsmMnc c_BssgpCellMnc := '03'H;	/* MNC: Celca (Socatel) */
 private template (value) BssgpCellId ts_BssgpCellIdDstAddr_default := {
 	ra_id := {
 		lai := {