runtime(doc): tweak documentation style a bit

closes: #15371

Signed-off-by: h-east <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index b921cb5..e2c6967 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1,4 +1,4 @@
-*eval.txt*	For Vim version 9.1.  Last change: 2024 Jul 17
+*eval.txt*	For Vim version 9.1.  Last change: 2024 Jul 28
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -3125,7 +3125,7 @@
 				let lconst[1][0] = 'b'  " OK
 <							*E995*
 			It is an error to specify an existing variable with
-			:const. >
+			|:const|. >
 				:let x = 1
 				:const x = 1  " Error!
 <							*E996*