patch 9.1.1374: completion: 'smartcase' not respected when filtering matches

Problem:  Currently, 'smartcase' is respected when completing keywords
          using <C-N>, <C-P>, <C-X><C-N>, and <C-X><C-P>. However, when
          a user continues typing and the completion menu is filtered
          using cached matches, 'smartcase' is not applied. This leads
          to poor-quality or irrelevant completion suggestions, as shown
          in the example below.
Solution: When filtering cached completion items after typing additional
          characters, apply case-sensitive comparison if 'smartcase' is
          enabled and the typed pattern includes uppercase characters.
          This ensures consistent and expected completion behavior.
          (Girish Palya)

closes: #17271

Signed-off-by: Girish Palya <girishji@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/insert.txt b/runtime/doc/insert.txt
index f52cf40..f3d92b2 100644
--- a/runtime/doc/insert.txt
+++ b/runtime/doc/insert.txt
@@ -1,4 +1,4 @@
-*insert.txt*    For Vim version 9.1.  Last change: 2025 Apr 14
+*insert.txt*    For Vim version 9.1.  Last change: 2025 May 08
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -1347,6 +1347,7 @@
 The 'pumwidth' option can be used to set a minimum width.  The default is 15
 characters.
 
+							*compl-states*
 There are three states:
 1. A complete match has been inserted, e.g., after using CTRL-N or CTRL-P.
 2. A cursor key has been used to select another match.  The match was not