patch 9.0.0627: "const" and "final" both make the type a constant

Problem:    "const" and "final" both make the type a constant. (Daniel
            Steinberg)
Solution:   Only have "const" make the type a constant.
diff --git a/src/vim.h b/src/vim.h
index 8f1bf33..14f67f7 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2250,6 +2250,7 @@
 } estack_arg_T;
 
 // Flags for assignment functions.
+#define ASSIGN_VAR	0     // ":var" (nothing special)
 #define ASSIGN_FINAL	0x01  // ":final"
 #define ASSIGN_CONST	0x02  // ":const"
 #define ASSIGN_NO_DECL	0x04  // "name = expr" without ":let"/":const"/":final"