chore: fix types & docs for upload credentials []

[2wce]

Summary

we were not exporting the types for the new upload credentials method. Our example for how to use the method was also out of date. This should be fixed now

Checklist (check all before merging)

• Both unit and integration tests are passing
• There are no breaking changes
• Changes are reflected in the documentation

When adding a new method:

• The new method is exported through the default and plain CMA client
• All new public types are exported from ./lib/export-types.ts
• Added a unit test for the new method
• Added an integration test for the new method
• The new method is added to the documentation

[contentful-automation]

🎉 This PR is included in version 11.38.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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