Remove type argument from WorkspaceVariableInput
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MR: Pending
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## Description
This is a follow up issue for https://gitlab.com/gitlab-org/gitlab/-/merge_requests/176617+ where we deprecated the `type` argument in favour of the new `variableType` on the graphQL `Type.WorkspaceVariableInput `
It was deprecated in `17.9` and would be eligible for removal in the major release `19.0` according to the deprecation process defined [here](https://docs.gitlab.com/api/graphql/#deprecation-and-removal-process)
We should remove all references of type from Graphql and the BE code for remote_development.
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## Acceptance criteria
- [ ] Removed from graphQL type `WorkspaceVariableInput`
- [ ] All references to the argument `type` should be replaced with `variableType` in the BE code
- [ ] References updated in specs as well
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