show-ref doc: fix carets in monospace

When commit 00bf685 (show-ref doc: update for internal consistency,
2023-05-19) switched from double quotes to backticks around our {caret}
macro, we started rendering "{caret}" literally. Fix this by replacing
by a "^" character.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Martin Ågren

Documentation/git-show-ref.txt

@@ -47,7 +47,7 @@ OPTIONS
 -d::
 --dereference::
 
-	Dereference tags into object IDs as well. They will be shown with `{caret}{}`
+	Dereference tags into object IDs as well. They will be shown with `^{}`
 	appended.
 
 -s::
@@ -78,7 +78,7 @@ OPTIONS
 	Make `git show-ref` act as a filter that reads refs from stdin of the
 	form `^(?:<anything>\s)?<refname>(?:\^{})?$`
 	and performs the following actions on each:
-	(1) strip `{caret}{}` at the end of line if any;
+	(1) strip `^{}` at the end of line if any;
 	(2) ignore if pattern is provided and does not head-match refname;
 	(3) warn if refname is not a well-formed refname and skip;
 	(4) ignore if refname is a ref that exists in the local repository;