Bug 35368: Add public to "Add a new checkout" in API documentation

Bug 35368: Add public to "Add a new checkout" in API documentation

Without this patch the "Add a new checkout" label showed
up twice in the Checkouts section of the API documentation.
This adds (public) to the end of one, to make it possible
to distinguish them.

To test (ON YOUR HOST MACHINE):
1. Run:
   $ cd api/v1/swagger
   $ docker run --rm -v $(pwd):/api --workdir /api redocly/cli \
           build-docs swagger.yaml --output index.html
2. Open the generated index.html in your browser
3. Verify doubled up headings
4. Apply patch
5. Re-run docker command form 1.
6. Verify there are now 2 different labels and "(public)" is on the
   right one.

Note: if you have wrong permissions on the file, chown it to your
own user to open it in the browser.

Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit dbc67ce351e00f71a55586c095895aafab067d72)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>