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/autocmd.txt b/runtime/doc/autocmd.txt
index 5d60fbe..01d718f 100644
--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -1,4 +1,4 @@
-*autocmd.txt*   For Vim version 8.1.  Last change: 2019 Apr 27
+*autocmd.txt*   For Vim version 8.1.  Last change: 2019 May 05
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -20,7 +20,6 @@
 10. Using autocommands		|autocmd-use|
 11. Disabling autocommands	|autocmd-disable|
 
-{Vi does not have any of these commands}
 
 ==============================================================================
 1. Introduction						*autocmd-intro*