fix: accept chunked ProGuard uploads

[jpnurmi]

Sentry CLI 3.x has dropped support for non-chunked ProGuard uploads. sentry-cli upload-proguard throws an error unless chunked ProGuard uploads are accepted:

Server does not support uploading ProGuard mappings via chunked upload. Please update your Sentry server.

See also:

• feat(proguard): Upload ProGuard with chunked uploading sentry-cli#2918
• https://github.com/getsentry/sentry-cli/blob/3.0.3/src/commands/upload_proguard.rs#L150-L156
• chore(deps): update CLI to v3.0.3 sentry-dotnet#4805

[github-actions]

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