patch 8.2.0017: OS/2 and MS-DOS are still mentioned

Problem:    OS/2 and MS-DOS are still mentioned, even though support was
            removed long ago.
Solution:   Update documentation. (Yegappan Lakshmanan, closes #5368)
diff --git a/runtime/gvimrc_example.vim b/runtime/gvimrc_example.vim
index fa0f685..cc3e791 100644
--- a/runtime/gvimrc_example.vim
+++ b/runtime/gvimrc_example.vim
@@ -6,7 +6,7 @@
 " Last change:	2016 Apr 05
 "
 " To use it, copy it to
-"     for Unix and OS/2:  ~/.gvimrc
+"	       for Unix:  ~/.gvimrc
 "	      for Amiga:  s:.gvimrc
 "  for MS-DOS and Win32:  $VIM\_gvimrc
 "	    for OpenVMS:  sys$login:.gvimrc