Upgrade SpringDoc to 2.6.0

[JohnNiang]

What type of PR is this?

/kind cleanup /area core /milestone 2.17.0

What this PR does / why we need it:

This PR upgrades SpringDoc to 2.6.0 and its gradle plugin to 1.9.0. See https://github.com/springdoc/springdoc-openapi/releases/tag/v2.6.0 and https://github.com/springdoc/springdoc-openapi-gradle-plugin/releases/tag/1.9.0 for more.

Does this PR introduce a user-facing change?

升级 SpringDoc 至 2.6.0

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 57.20%. Comparing base (bc10336) to head (7ce6988). Report is 37 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #6227 +/- ## ============================================ + Coverage 54.51% 57.20% +2.69% - Complexity 3523 3719 +196 ============================================ Files 646 647 +1 Lines 21862 21968 +106 Branches 1528 1536 +8 ============================================ + Hits 11917 12566 +649 + Misses 9328 8793 -535 + Partials 617 609 -8 ```

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[f2c-ci-robot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ruibaby

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