docs: fix misleading example for urlPrefix

The default value for protocols.swift.urlPrefix is "swift", which makes
the Swift API available at http://host:port/swift/v1. However, in the
documentation our example says "/swift", which resulted in the
unexpected endpoint http://host:port//swift/v1.

Apparently, Ceph distinguishes between both values even though their
docs[1] seem to suggest that using leading slashes is fine.

This commit fixes the examples in the documentation to use the default
value "swift".

[1]
https://docs.ceph.com/en/reef/radosgw/config-ref/#confval-rgw_swift_url_prefix

Fixes #15065

Signed-off-by: Silvio Ankermann <silvio.ankermann@cloudandheat.com>
(cherry picked from commit fcce3ca520)

Documentation/Storage-Configuration/Object-Storage-RGW/ceph-object-swift.md

@@ -76,7 +76,7 @@ spec:
   protocols:
     swift:
       accountInUrl: true
-      urlPrefix: /swift
+      urlPrefix: swift
     # note that s3 is enabled by default if protocols.s3.enabled is not explicitly set to false
   preservePoolsOnDelete: true
   gateway: