Fix ab test export warning

[Jakeii]

What does this change?

Fix the warning showing in the console, the export wasn't updated in index.ts of ab-testing when changed in #14684 as there was a mysterious @ts-ignore there. Everything works without the ts-ignore so I've removed it, perhaps it was needed in the past?

Why?

Annoying warning, the export is not currently used anywhere, which is why this didn't show up as a linting error. And wouldn't have any implications beyond the warning.

ModuleDependencyWarning: export 'ABTests' (reexported as 'ABTests') was not found in './abTest.ts' (possible exports: activeABtests, allABTests)

[github-actions]

Deploy build 64 of dotcom:ab-testing to CODE

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• Deploy build 64 of dotcom:ab-testing to CODE
• Deploy parts of build 64 to CODE by previewing it first
• What's on CODE right now?

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From guardian/actions-riff-raff.

[github-actions]

Deploy build 21840 of dotcom:rendering-all to CODE

All deployment options

• Deploy build 21840 of dotcom:rendering-all to CODE
• Deploy parts of build 21840 to CODE by previewing it first
• What's on CODE right now?

---

From guardian/actions-riff-raff.

[github-actions]

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