fix(doc): resolve example error for `oras tag`

[qweeah]

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged): Fixes #1418

Please check the following list:

• [ ] Does the affected code have corresponding tests, e.g. unit test, E2E test?
• [ ] Does this change require a documentation update?
• [ ] Does this introduce breaking changes that would require an announcement or bumping the major version?
• [ ] Do all new files have an appropriate license header?

[codecov[bot]]

Codecov Report

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

Project coverage is 85.33%. Comparing base (0bbd881) to head (ad381b4).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1419 +/- ## ========================================== + Coverage 85.28% 85.33% +0.05% ========================================== Files 106 106 Lines 3798 3798 ========================================== + Hits 3239 3241 +2 + Misses 335 333 -2 Partials 224 224 ```

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