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/syntax.txt b/runtime/doc/syntax.txt
index ed72830..c33b356 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.1.  Last change: 2025 Apr 28
+*syntax.txt*	For Vim version 9.1.  Last change: 2025 May 10
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -5991,6 +5991,12 @@
 TabLineFill	Tab pages line, where there are no labels.
 							*hl-TabLineSel*
 TabLineSel	Tab pages line, active tab page label.
+							*hl-TabPanel*
+TabPanel	TabPanel, not active tab page label.
+							*hl-TabPanelFill*
+TabPanelFill	TabPanel, where there are no labels.
+							*hl-TabPanelSel*
+TabPanelSel	TabPanel, active tab page label.
 							*hl-Terminal*
 Terminal	|terminal| window (see |terminal-size-color|).
 							*hl-Title*