preview:duration effect was shortened to preview:du when uploading a video

## Bug report for Cloudinary Ruby SDK
v1.28.0

## Describe the bug in a sentence or two.
Issue - preview:duration effect was shortened to preview:du when uploading a video using `Cloudinary::Uploader.upload`

Error - CloudinaryException: Eager Invalid effect in transformation: du_15.0

## Issue Type (Can be multiple)
- [ ] Build - Cannot install or import the SDK
- [ ] Performance - Performance issues
- [ ] Behaviour - Functions are not working as expected (such as generate URL)
- [ ] Documentation - Inconsistency between the docs and behaviour
- [ ] Other (Specify)

## Steps to reproduce
## Error screenshots or Stack Trace (if applicable)
…

## Operating System
- [ ] Linux
- [ ] Windows
- [ ] macOS
- [ ] All

## Environment and Libraries (fill in the version numbers)
- Cloudinary Ruby SDK version - 1.28.0
- Ruby Version - 3.2.1
- Rails Version - 6.1.7.4
- Other Libraries (Carrierwave, ActiveStorage, etc) - 6.1.7.4

## Repository

If possible, please provide a link to a reproducible repository that showcases the problem

Comienza en Cloudinary::Uploader.upload y reproduce la carga de vídeo reportada con las versiones indicadas de SDK y Ruby, comprobando dónde preview:duration se convierte en preview:du. El issue no indica ningún archivo ni prueba; se considera completado cuando se conserva el nombre completo del efecto y la carga deja de devolver el error du_15.0 invalid-effect.

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