patch 8.2.2566: Vim9: Function name is not recognized

Problem:    Vim9: Function name is not recognized.
Solution:   Change lookup_scriptvar() to also find function names.
            (closes #7770)
diff --git a/src/vim9script.c b/src/vim9script.c
index 68d7f5e..5ce7c3b 100644
--- a/src/vim9script.c
+++ b/src/vim9script.c
@@ -138,7 +138,7 @@
     }
 
     eap->cmd = eap->arg;
-    (void)find_ex_command(eap, NULL, lookup_scriptvar, NULL);
+    (void)find_ex_command(eap, NULL, lookup_scriptitem, NULL);
     switch (eap->cmdidx)
     {
 	case CMD_let: