patch 8.2.0286: cannot use popup_close() for a terminal popup

Problem:    Cannot use popup_close() for a terminal popup.
Solution:   Allow using popup_close(). (closes #5666)
diff --git a/runtime/doc/popup.txt b/runtime/doc/popup.txt
index 55565bc..5122994 100644
--- a/runtime/doc/popup.txt
+++ b/runtime/doc/popup.txt
@@ -1,4 +1,4 @@
-*popup.txt*  For Vim version 8.2.  Last change: 2020 Feb 05
+*popup.txt*  For Vim version 8.2.  Last change: 2020 Feb 20
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -148,6 +148,8 @@
 - The popup window always has focus, it is not possible to switch to another
   window.
 - When the job ends, the popup window closes.
+- The popup window can be closed with `popup_close()`, the terminal buffer
+  then becomes hidden.
 - The default Pmenu color is only used for the border and padding.  To change
   the color of the terminal itself set 'wincolor'.