patch 8.1.1280: remarks about functionality not in Vi clutters the help

Problem:    Remarks about functionality not in Vi clutters the help.
Solution:   Move all info about what is new in Vim or already existed in Vi to
            vi_diff.txt.  Remove {not in Vi} remarks. (closes #4268) Add
            "noet" to the help files modeline.  Also include many other help
            file improvements.
diff --git a/runtime/doc/mbyte.txt b/runtime/doc/mbyte.txt
index 15198f6..7b8c21f 100644
--- a/runtime/doc/mbyte.txt
+++ b/runtime/doc/mbyte.txt
@@ -1,4 +1,4 @@
-*mbyte.txt*     For Vim version 8.1.  Last change: 2018 Jan 21
+*mbyte.txt*     For Vim version 8.1.  Last change: 2019 Apr 28
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar et al.