patch 8.2.4615: mapping with escaped bar does not work in :def function

Problem:    Mapping with escaped bar does not work in :def function. (Sergey
            Vlasov)
Solution:   Do not remove the backslash. (closes #10002)
diff --git a/src/vim9cmds.c b/src/vim9cmds.c
index 072a106..483b1f3 100644
--- a/src/vim9cmds.c
+++ b/src/vim9cmds.c
@@ -1848,7 +1848,7 @@
 	if ((argt & EX_TRLBAR) && !usefilter)
 	{
 	    eap->argt = argt;
-	    separate_nextcmd(eap);
+	    separate_nextcmd(eap, TRUE);
 	    if (eap->nextcmd != NULL)
 		nextcmd = eap->nextcmd;
 	}