patch 9.1.1391: Vim does not have a vertical tabpanel

Problem:  Vim does not have a tabpanel
Solution: include the tabpanel feature
          (Naruhiko Nishino, thinca)

closes: #17263

Co-authored-by: thinca <thinca@gmail.com>
Signed-off-by: Naruhiko Nishino <naru123456789@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/index.txt b/runtime/doc/index.txt
index 024102c..00a09ae 100644
--- a/runtime/doc/index.txt
+++ b/runtime/doc/index.txt
@@ -1,4 +1,4 @@
-*index.txt*     For Vim version 9.1.  Last change: 2025 Mar 18
+*index.txt*     For Vim version 9.1.  Last change: 2025 May 14
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -1583,6 +1583,7 @@
 |:redraw|	:redr[aw]	  force a redraw of the display
 |:redrawstatus|	:redraws[tatus]	  force a redraw of the status line(s)
 |:redrawtabline|  :redrawt[abline]  force a redraw of the tabline
+|:redrawtabpanel| :redrawtabp[anel] force a redraw of the tabpanel
 |:registers|	:reg[isters]	display the contents of registers
 |:resize|	:res[ize]	change current window height
 |:retab|	:ret[ab]	change tab size