runtime(doc): fix typos.

* Fix typo in document (Related: #12516)
* Fix E1363 duplication
* Fix one more typo.

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/pattern.txt b/runtime/doc/pattern.txt
index 9e048ff..4fa26e0 100644
--- a/runtime/doc/pattern.txt
+++ b/runtime/doc/pattern.txt
@@ -1080,7 +1080,7 @@
 
 \(\)	A pattern enclosed by escaped parentheses.	*/\(* */\(\)* */\)*
 	E.g., "\(^a\)" matches 'a' at the start of a line.
-	There can only be ten of these.  You can use "\%(" to add more, but
+	There can only be nine of these.  You can use "\%(" to add more, but
 	not counting it as a sub-expression.
 	*E51* *E54* *E55* *E872* *E873*