Add migration to fix urls on TranslationContext model

[jhonatan-lopes]

Description

Fixes cases where editors couldn't edit translations because wagtail-localize was trying to get URL on linkbutton blocks, which doesn't exist anymore.

The remnants were found on the TranslationContext model, which saves the field's path on field and field_path. Because this had explicit references to URL that weren't migrated, it caused the KeyError.

Link to sample test page: http://localhost:8000/cms/pages/27553/edit/
Related PRs/issues:

• Cannot edit translation for BlogPage #12074
• https://mozilla-hub.atlassian.net/browse/TP-367

Checklist

Tests

• Is the code I'm adding covered by tests?

Changes in Models:

• Did I update or add new fake data?
• Did I squash my migration?
• Are my changes backward-compatible. If not, did I schedule a deploy with the rest of the team?

Documentation:

• Is my code documented?
• Did I update the READMEs or wagtail documentation?

Merge Method
💡❗Remember to use squash merge when merging non-feature branches into main

┆Issue is synchronized with this Jira Story

[robdivincenzo]

LGTM 🚀, thanks @jhonatan-lopes !