Fix #1264 bolt-http4k fails to parse a request with duplicated header lines

[seratch]

This pull request resolves #1264

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

• [ ] bolt (Bolt for Java)
• [x] bolt-{sub modules} (Bolt for Java - optional modules)
• [ ] 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

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you agree to those rules.

[codecov[bot]]

Codecov Report

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

Comparison is base (5afc51b) 74.32% compared to head (a208e08) 74.31%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1266 +/- ## ============================================ - Coverage 74.32% 74.31% -0.01% + Complexity 4121 4120 -1 ============================================ Files 443 443 Lines 13078 13083 +5 Branches 1322 1323 +1 ============================================ + Hits 9720 9723 +3 - Misses 2586 2587 +1 - Partials 772 773 +1 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.