patch 8.2.3835: the inline-function example does not work

Problem:    The inline-function example does not work.
Solution:   Drop ":let".  Add EX_EXPR_ARG to CMD_var. (issue #9352)
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index c2657b0..044580a 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -1691,7 +1691,7 @@
 	EX_RANGE|EX_WHOLEFOLD|EX_EXTRA|EX_DFLALL|EX_CMDWIN|EX_LOCK_OK|EX_NONWHITE_OK,
 	ADDR_LINES),
 EXCMD(CMD_var,		"var",		ex_var,
-	EX_EXTRA|EX_NOTRLCOM|EX_SBOXOK|EX_CMDWIN|EX_LOCK_OK,
+	EX_EXTRA|EX_NOTRLCOM|EX_EXPR_ARG|EX_SBOXOK|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_NONE),
 EXCMD(CMD_version,	"version",	ex_version,
 	EX_EXTRA|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,