Update version for the next release (v0.28.0)

[meili-bot]

This PR is auto-generated.

The automated script updates the version of meilisearch-go to a new version: "v0.28.0"

[codecov[bot]]

Codecov Report

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

Project coverage is 86.73%. Comparing base (a5a58fb) to head (f43c8a9). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #567 +/- ## ======================================= Coverage 86.73% 86.73% ======================================= Files 11 11 Lines 2043 2043 ======================================= Hits 1772 1772 Misses 165 165 Partials 106 106 ```

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[meili-bors[bot]]

Build succeeded:

• integration-tests (go current version)
• integration-tests (go latest version)
• linter