patch 9.1.1426: completion: register contents not completed

Problem:  CTRL-X CTRL-R only completes individual words from registers,
          making it difficult to insert complete register content.
Solution: Add consecutive CTRL-X CTRL-R support - first press completes
          words, second press completes full register lines, similar to
          CTRL-X CTRL-L and CTRL-X CTRL-P behavior (glepnir).

closes: #17395

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/index.txt b/runtime/doc/index.txt
index d03d81e..ff27994 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 May 26
+*index.txt*     For Vim version 9.1.  Last change: 2025 Jun 02
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -163,7 +163,7 @@
 |i_CTRL-X_CTRL-N|	CTRL-X CTRL-N	next completion
 |i_CTRL-X_CTRL-O|	CTRL-X CTRL-O	omni completion
 |i_CTRL-X_CTRL-P|	CTRL-X CTRL-P	previous completion
-|i_CTRL-X_CTRL-R|	CTRL-X CTRL-R	complete words from registers
+|i_CTRL-X_CTRL-R|	CTRL-X CTRL-R	complete contents from registers
 |i_CTRL-X_CTRL-S|	CTRL-X CTRL-S	spelling suggestions
 |i_CTRL-X_CTRL-T|	CTRL-X CTRL-T	complete identifiers from thesaurus
 |i_CTRL-X_CTRL-Y|	CTRL-X CTRL-Y	scroll down