fix(upload): ssh-deploy-on-explicit-save: incorrect type

According to upstream package emacs-ssh-deploy, the value 0 should
disable the auto-save behavior. As the ssh-deploy-on-explicit-save is
considered true if its value is 0, it triggers the after-save-hook
anyway. This commit fixes the hook so it conforms to upstream
definition:

  ssh-deploy-on-explicit-save Enabled automatic uploads on save (integer)

Co-authored-by: visika <visika@users.noreply.github.com>
Close: #7513
Fix: #7512

modules/tools/upload/README.org

@@ -47,7 +47,7 @@ to establish this mapping. E.g.
 #+begin_src emacs-lisp
 ((nil . ((ssh-deploy-root-local . "/local/path/to/project")
          (ssh-deploy-root-remote . "/ssh:user@server:/remote/project/")
-         (ssh-deploy-on-explicit-save . t))))
+         (ssh-deploy-on-explicit-save . 1))))
 #+end_src
 
 #+begin_quote