[FEATURE] Don't constrain transformers upper bound to version 5

[markbackman]

Which SDK is this feature request for?

• speechmatics-rt (Real-Time SDK)
• speechmatics-batch (Batch SDK)
• Both SDKs
• General/Repository
• speechmatics-voice (Python SDK)

Is your feature request related to a problem? Please describe.
The speechmatics-voice SDK constrains transformers to an upper bound of version 5. This prevents other packages from using transformers >=5 when installing speechmatics-voice.

Describe the solution you'd like
Increase or remove the transformers upper bound.

Describe alternatives you've considered
None. transformers is a core dep that I can't work around.

Use case
Describe the specific use case or scenario where this feature would be beneficial:
Use speechmatics-voice with other models that use transformers.

Related issues/PRs
Link any related issues or pull requests:

• Closes #
• Related to #

Priority/Impact
How important is this feature to you?

• Critical - blocking current work
• High - would significantly improve workflow
• Medium - nice to have improvement
• Low - minor enhancement