docs(api): drop trailing slash on podman.io/community contact URL

The swagger spec generated from pkg/api/server/doc.go sets the contact
URL to https://podman.io/community/. That URL now returns 404, while
https://podman.io/community (no trailing slash) returns 200 and is what
the live site links to from its own navigation. Issue #28298 reports
the link as broken at the top of the rendered API reference, which is
where ReDoc surfaces the contact field.

Drop the trailing slash so the contact link in the generated swagger
spec resolves.

Signed-off-by: Matt Van Horn <mvanhorn@gmail.com>