Update data-tests.md (#5565)

adds a pagination next to unit tests as the user was getting stuck in a
loop bc the 'next' page was taking them to the same page they're on:
data tests

Resolves #5542

## What are you changing in this pull request and why?
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Adding or removing pages (delete if not applicable):
- [ ] Add/remove page in `website/sidebars.js`
- [ ] Provide a unique filename for new pages
- [ ] Add an entry for deleted pages in `website/vercel.json`
- [ ] Run link testing locally with `npm run build` to update the links
that point to deleted pages

website/docs/docs/build/data-tests.md

@@ -2,6 +2,8 @@
 title: "Add data tests to your DAG"
 sidebar_label: "Data tests"
 description: "Read this tutorial to learn how to use data tests when building in dbt."
+pagination_next: "docs/build/unit-tests"
+pagination_prev: null
 search_weight: "heavy"
 id: "data-tests"
 keywords: