[DOCS] Changes to the docs API page

[deborahniesz]

Description

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Changes consist of:

• Rename API tab to GX API and change styles of default index page to match the styles of the auto-generated index page
• Remove next button from navigation in API overview page (and the "was this helpful" component)
• Fix link to API page so that you can access the API page directly after clicking GX API instead of having to double click.
• Change in the breadcrumbs, from now on every breadcrumb that has only one element (therefore not clickable) will be hidden

Previous way to interact with the API index page

oldAPIpage.mp4

Current way to interact with the API index page

newAPIpage.mp4

• Description of PR changes above includes a link to an existing GitHub issue
• PR title is prefixed with one of: [BUGFIX], [FEATURE], [DOCS], [MAINTENANCE], [CONTRIB]
• Code is linted - run invoke lint (uses ruff format + ruff check)
• Appropriate tests and docs have been updated

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[josectobar]

Looks great, thanks!