Switch JWT page from sidebar entry to floating-pages exception

The JWT auth page is Cloud-only while its siblings under External
Authenticators in the sidebar are self-managed-only, so listing it
alongside them mis-routes Cloud readers and broke `DocsCheck`.

Revert the sidebar addition and add the page to
`plugins/floating-pages-exceptions.txt` instead — same as other
intentionally-out-of-nav pages such as `cloud/features/backups/faq.md`.
The page remains reachable from `operations/external-authenticators/index.md`,
which lists it as the JWT authenticator entry.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: kcmannem

plugins/floating-pages-exceptions.txt

@@ -13,3 +13,4 @@ integrations/data-ingestion/clickpipes/postgres/maintenance.md
 operations/utilities/clickhouse-keeper-http-api.md
 cloud/features/backups/faq.md
 interfaces/web-terminal
+operations/external-authenticators/jwt.md

sidebars.js

@@ -1630,7 +1630,6 @@ const sidebars = {
             },
             'operations/external-authenticators/http',
             'operations/external-authenticators/kerberos',
-            'operations/external-authenticators/jwt',
           ],
         },
       ],