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/pi_gzip.txt b/runtime/doc/pi_gzip.txt
index 6017efa..1631e2e 100644
--- a/runtime/doc/pi_gzip.txt
+++ b/runtime/doc/pi_gzip.txt
@@ -1,4 +1,4 @@
-*pi_gzip.txt*   For Vim version 8.1.  Last change: 2016 Nov 06
+*pi_gzip.txt*   For Vim version 8.1.  Last change: 2019 May 05
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -13,8 +13,6 @@
 You can avoid loading this plugin by setting the "loaded_gzip" variable: >
 	:let loaded_gzip = 1
 
-{Vi does not have any of this}
-
 ==============================================================================
 1. Autocommands						*gzip-autocmd*