Update error view layout and constraints on iPad for non-WordPress sites and when Jetpack is not installed

[pmusolino]

Closes: #13813

Description

This PR updates the layout and constraints for the ULErrorViewController to improve the alignment and appearance of error views, for iPad devices. The changes address misaligned views and refine the layout for better visual consistency.

• Removed some unused stack view constraints.
• Refactored constraints to improve layout consistency and avoid ambiguity.

Steps to reproduce

Using iPad simulator

Case 1

1. Log in to an existing testing store with Jetpack.
2. Navigate to menu.
3. Tap on the store (first row).
4. Press “Connect existing store”
5. Add a store that doesn’t exist (eg. example.com).
6. Notice that the view telling you that the site is not a WordPress site is not centered.

Case 2

1. Log in to an existing testing store with Jetpack.
2. Create a testing jurassic ninja site with Woo installed but without Jetpack.
3. Navigate to menu.
4. Tap on the store (first row).
5. Press “Connect existing store”
6. Add the jurassic ninja store that you created.
7. Notice that the view telling you to install Jetpack is not centered.

Testing information

I just tested following the steps to reproduce above, and now the view is centered.

Screenshots

Before	After

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Reviewer (or Author, in the case of optional code reviews):

Please make sure these conditions are met before approving the PR, or request changes if the PR needs improvement:

• The PR is small and has a clear, single focus, or a valid explanation is provided in the description. If needed, please request to split it into smaller PRs.
• Ensure Adequate Unit Test Coverage: The changes are reasonably covered by unit tests or an explanation is provided in the PR description.
• Manual Testing: The author listed all the tests they ran, including smoke tests when needed (e.g., for refactorings). The reviewer confirmed that the PR works as expected on all devices (phone/tablet) and no regressions are added.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce iOS by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS
	Build Number	pr13991-7ba28d4
	Version	20.4
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	7ba28d4
	App Center Build	WooCommerce - Prototype Builds #10907

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