release version 9.0

Problem:    About time to release Vim 9.0.
Solution:   Update the version number everywhere.
diff --git a/runtime/doc/todo.txt b/runtime/doc/todo.txt
index 35a7c69..896be45 100644
--- a/runtime/doc/todo.txt
+++ b/runtime/doc/todo.txt
@@ -1,4 +1,4 @@
-*todo.txt*      For Vim version 8.2.  Last change: 2022 Jun 27
+*todo.txt*      For Vim version 9.0.  Last change: 2022 Jun 27
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar