patch 8.2.1471: :const only locks the variable, not the value

Problem:    :const only locks the variable, not the value.
Solution:   Lock the value as ":lockvar 1 var" would do. (closes #6719)
diff --git a/src/version.c b/src/version.c
index b96a49f..7e660d8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1471,
+/**/
     1470,
 /**/
     1469,