Switch `_transcoding` to `transcoding`

[ankatiyar]

Description

I noticed the kedro-viz was throwing deprecation warnings for TRANSCODING_SEPARATOR when trying it with Kedro from the main branch - This is due to this PR https://github.com/kedro-org/kedro/pull/3826 This change will be released in Kedro 0.19.6

Development notes

QA notes

Checklist

• [ ] Read the contributing guidelines
• [ ] Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• [ ] Updated the documentation to reflect the code changes
• [ ] Added new entries to the RELEASE.md file
• [ ] Added tests to cover my changes

[rashidakanchwala]

thank you so much. You are a ⭐ @ankatiyar

[rashidakanchwala]

I think this will not work with Kedro 0.19.4 and 0.19.5. Let's discuss @ankatiyar

[ankatiyar]

Closing this in favour of #1928 as discussed offline with @rashidakanchwala