docs: update e2e best practices link in readme (#11757)

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## **Description**

This pull request updates the outdated end-to-end best practices link in
the testing section of the README, pointing it to the latest contributor
docs for accurate reference.




## **Related issues**

Fixes:

## **Manual testing steps**

1. Go to this page...
2.
3.

## **Screenshots/Recordings**

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### **Before**

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### **After**

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## **Pre-merge author checklist**

- [ ] I’ve followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
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guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

docs/readme/testing.md

@@ -357,4 +357,4 @@ Our CI/CD process is automated through various Bitrise pipelines, each designed
 
 ### Best Practices
 
-For more guidelines and best practices, refer to our [Best Practices Document](https://github.com/MetaMask/contributor-docs/blob/main/docs/e2e-testing.md).
+For more guidelines and best practices, refer to our [Best Practices Document](https://github.com/MetaMask/contributor-docs/blob/main/docs/testing/e2e-testing.md).