Fix constraint conflict in LinkEmailElement (#5822)

## Summary
<!-- Simple summary of what was changed. -->

This pull request fixes an unsatisfiable constraint in
`LinkEmailElement`.

## Motivation
<!-- Why are you making this change? If it's for fixing a bug, if
possible, please include a code snippet or example project that
demonstrates the issue. -->


[RUN_MOBILESDK-4562](https://jira.corp.stripe.com/browse/RUN_MOBILESDK-4562)

## Testing
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<!-- Ignored Tests: Did you newly ignore a test in this PR? If so,
please open an R4 incident so that the test can be re-enabled as soon as
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<details><summary>Before</summary>
<p>


https://github.com/user-attachments/assets/95567b54-ab80-4c00-9b0d-f037dac834d8

</p>
</details>

<details><summary>After</summary>
<p>


https://github.com/user-attachments/assets/2dee1416-42b3-4835-807d-8e8e5bc6b2b0

</p>
</details>

## Changelog
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    - [Added] for new features.
    - [Changed] for changes in existing functionality.
    - [Deprecated] for soon-to-be removed features.
    - [Removed] for now removed features.
    - [Fixed] for any bug fixes.
    - [Security] in case of vulnerabilities.
-->
N/A

Author: tillh-stripe

Example/PaymentSheet Example/PaymentSheet Example/AppDelegate+BrokenConstraints.swift

@@ -36,7 +36,6 @@ extension AppDelegate {
         // Ignore broken constraints that existed at the time of writing this - please try to fix newly introduced ones instead of ignoring!
         // Sometimes the broken constraint references something that is unique, in which case we can ignore it easily
         let ignoredBrokenConstraints = [
-            "STP_Internal_LinkMoreInfoView", // https://jira.corp.stripe.com/browse/RUN_MOBILESDK-4562
             "verticalSeparatorWidth' separator|.width == 0.333333", // Apple broken UIAlert constraint - oddly they never log this either; maybe they also have an ignorelist!
             "UISV-spacing' H:[_UIInterfaceActionCustomViewRepresentationView:", // Same as ^
             "_UIModernBarButton:", // iOS 26+ keyboard toolbar issue

StripePaymentSheet/StripePaymentSheet/Source/Internal/Link/Elements/LinkEmailElement.swift

@@ -42,8 +42,9 @@ class LinkEmailElement: Element {
             trailing: theme.textFieldInsets.trailing
         )
         if let infoView = infoView {
+            // Use stack view's custom spacing instead of manual constraints to avoid conflicts
+            stackView.setCustomSpacing(ElementsUI.contentViewInsets.trailing, after: activityIndicator)
             NSLayoutConstraint.activate([
-                activityIndicator.trailingAnchor.constraint(equalTo: infoView.leadingAnchor, constant: -ElementsUI.contentViewInsets.trailing),
                 infoView.widthAnchor.constraint(equalToConstant: LinkMoreInfoView.Constants.logoWidth),
             ])
         }