[Improve][Docs] Iceberg connector adds parameter documentation related to Kerberos authentication

[chl-wxp]

Purpose of this pull request

Does this PR introduce any user-facing change?

How was this patch tested?

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If necessary, please update incompatible-changes.md to describe the incompatibility caused by this PR.
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config

[DanielLeens]

I pulled this locally as a docs-only change and checked the added Iceberg Kerberos parameters against the current option names used in code.

From my side, the patch is doing the right thing: it is documenting existing Kerberos-related options in the Iceberg source/sink docs, and the EN / ZH docs are updated together.

I do not see a blocker here.

[davidzollo]

+1
Good job

[zhangshenghang]

+1