Fix #1233 files.upload v2 import error

[seratch]

This pull request resolves #1233 for the main branch. I will make the same change for a hotfix too

Category (place an x in each of the [ ])

• [ ] bolt (Bolt for Java)
• [ ] bolt-{sub modules} (Bolt for Java - optional modules)
• [x] slack-api-client (Slack API Clients)
• [ ] slack-api-model (Slack API Data Models)
• [ ] *slack-api--kotlin-extension** (Kotlin Extensions for Slack API Clients)
• [ ] slack-app-backend (The primitive layer of Bolt for Java)

Requirements

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[codecov[bot]]

Codecov Report

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

Comparison is base (9e9d7da) 74.04% compared to head (097e3fb) 74.04%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1234 +/- ## ========================================= Coverage 74.04% 74.04% Complexity 4083 4083 ========================================= Files 440 440 Lines 12995 12995 Branches 1310 1310 ========================================= Hits 9622 9622 Misses 2606 2606 Partials 767 767 ```

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