Remove deprecated devfile_web_url from GraphQL API
MR: Pending
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## Description
We would need to remove the deprecated `devfile_web_url` field from GraphQL `workspace_type`. Pls see discussion and MR [here](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/171230#note_2199857965) for reference.
The field would be deprecated in GitLab release 17.8, and based on the deprecation process, https://gitlab.com/gitlab-org/gitlab/-/blob/master/doc/api/graphql/index.md#deprecation-and-removal-process. The earliest removal release would be 19.0
## Acceptance Criteria
- [ ] Remove deprecated `devfile_web_url` field from GraphQL `workspace_type`
- [ ] Remove deprecated `devfile_web_url` method from workspace model
- [ ] Remove API doc references for this field
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