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/diff.txt b/runtime/doc/diff.txt
index 0dbc7f8..069a853 100644
--- a/runtime/doc/diff.txt
+++ b/runtime/doc/diff.txt
@@ -1,4 +1,4 @@
-*diff.txt*      For Vim version 9.1.  Last change: 2024 Mar 26
+*diff.txt*      For Vim version 9.1.  Last change: 2024 Mar 28
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -243,12 +243,11 @@
 				highlight the exact difference between the
 				two.  Will respect any 'diffopt' flag that
 				affects internal diff.
-				Not used when `inline:` set to "none".
-|hl-DiffTextAdd|  DiffTextAdd	Added text inside a Changed line. Similar to
+				Not used when `inline:` is set to "none".
+|hl-DiffTextAdd|  DiffTextAdd	Added text inside a Changed line.  Similar to
 				DiffText, but used when there is no
-				corresponding text in other buffers.  Will not
-				be used when `inline:` is set to "simple" or
-				"none".
+				corresponding text in other buffers.  Not used
+				when `inline:` is set to "simple" or "none".
 |hl-DiffDelete|	DiffDelete	Deleted lines.  Also called filler lines,
 				because they don't really exist in this
 				buffer.