runtime(doc): document that :b cannot handle buffer names starting with "+"

closes: #17229

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/windows.txt b/runtime/doc/windows.txt
index db24e51..545a44b 100644
--- a/runtime/doc/windows.txt
+++ b/runtime/doc/windows.txt
@@ -1,4 +1,4 @@
-*windows.txt*   For Vim version 9.1.  Last change: 2025 Jan 02
+*windows.txt*   For Vim version 9.1.  Last change: 2025 Apr 30
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -1289,7 +1289,9 @@
 		name also works, so long as it is unique in the list of
 		buffers.
 		Note that a buffer whose name is a number cannot be referenced
-		by that name; use the buffer number instead.
+		by that name; use the buffer number instead.  Same is true if
+		the buffer name starts with a `+`, it will be interpreted as
+		the start of a |+cmd|.
 		Insert a backslash before a space in a buffer name.
 		See |:buffer-!| for [!].
 		This will also edit a buffer that is not in the buffer list,