Rename Project 'Terraform' menu to 'Terraform states'

What does this MR do and why?

Part of menu reorganization in #393190+s

We need to rename the Terraform menu in the project's navigation to 'Terraform states', in order to respect the new menu structure defined in https://gitlab.com/gitlab-org/gitlab/-/issues/393190(expand the Projects section in the description), and see this comment for more details.

Closes #404387 (closed)

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Current navigation

Before	After

New navigation

Before	After

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