Fix webview retain cycle in special error pages handler and Expired certificate UI Test

[alessandroboron]

Task/Issue URL: https://app.asana.com/0/414709148257752/1209348984855251

Description:

This PR addresses:

• Fix web view retain cycle in SpecialErrorPageNavigationHandler by weakly retaining the webView.
• Fix Expired Certificate UI test broken due to icon logic changes for Malicious Site Protection

Steps to test this PR:

Retain Cycle

1. Launch debug version.
2. Open SERP.
3. Long press on any result.
4. Select "Open in background”.
5. Ensure deallocation assertion is not fired.

UI Test

1. Ensure Expired Certificate UI test pass.

Definition of Done (Internal Only):

• Does this PR satisfy our Definition of Done?

Copy Testing:

• Use of correct apostrophes in new copy, ie ’ rather than '

Orientation Testing:

• Portrait
• Landscape

Device Testing:

• iPhone SE (1st Gen)
• iPhone 8
• iPhone X
• iPhone 14 Pro
• iPad

OS Testing:

• iOS 15
• iOS 16
• iOS 17

Theme Testing:

• Light theme
• Dark theme

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Internal references:

Software Engineering Expectations
Technical Design Template

[dus7]

LGTM. Thanks!