patch 9.1.1252: typos in code and docs related to 'diffopt' "inline:"

Problem:  Typos in code and docs related to 'diffopt' "inline:".
          (after v9.1.1243)
Solution: Fix typos and slightly improve the docs.
          (zeertzjq)

closes: #16997

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 0b7ba91..84deeca 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt*	For Vim version 9.1.  Last change: 2025 Mar 27
+*options.txt*	For Vim version 9.1.  Last change: 2025 Mar 28
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2982,8 +2982,8 @@
 				none    Do not perform inline highlighting.
 				simple  Highlight from first different
 					character to the last one in each
-					line. This is the default if nothing
-					is set.
+					line.  This is the default if no
+					`inline:` value is set.
 				char    Use internal diff to perform a
 					character-wise diff and highlight the
 					difference.