feat: add patch endpoint to update transcript providers

[BrandonHBodine]

What this does:
This PR adds a DRF Patch endpoint for updating the "provider" field on VideoTranscript records.

Context:
When 2u/Edx wanted to add ai-translated content to the platform part of the project was translating the video transcripts. During the creation of the translated transcripts they were labeled with the provider="Custom" which has turned out to be too broad for some of the use cases Edx is looking to build out. We have since added a new provider in this repo and are looking to apply it with this change.

The status of the translated transcripts live in an external service (IDA in edx terms) and needs access to edx-val via the REST interface which is the core reason behind this change.

This is in regards to the following 2U ticket.
https://2u-internal.atlassian.net/browse/AU-2381

[codecov]

Codecov Report

Attention: Patch coverage is 14.81481% with 23 lines in your changes missing coverage. Please review.

Project coverage is 93.91%. Comparing base (b7c5db6) to head (7bad64b).

Files with missing lines	Patch %	Lines
edxval/views.py	12.50%	14 Missing ⚠️
edxval/api.py	10.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #562      +/-   ##
==========================================
- Coverage   94.58%   93.91%   -0.68%     
==========================================
  Files          32       32              
  Lines        3178     3204      +26     
  Branches      122      126       +4     
==========================================
+ Hits         3006     3009       +3     
- Misses        154      177      +23     
  Partials       18       18              

Flag	Coverage Δ
unittests	93.91% <14.81%> (-0.68%)	⬇️

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