org-manual: Suggest kbd macro for bindings

* doc/org-manual.org (Capture templates): Suggest kbd macro for
bindings.

doc/org-manual.org

@@ -7417,7 +7417,7 @@ going through the interactive template selection, you can create your
 key binding like this:
 
 #+begin_src emacs-lisp
-(define-key global-map "\C-cx"
+(define-key global-map (kbd "C-c x")
   (lambda () (interactive) (org-capture nil "x")))
 #+end_src