patch 8.2.1436: function implementing :substitute has unexpected name

Problem:    Function implementing :substitute has unexpected name.
Solution:   Rename from do_sub() to ex_substitute().
diff --git a/src/version.c b/src/version.c
index f764e98..d4b0afa 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1436,
+/**/
     1435,
 /**/
     1434,