Accessibility - Narrator down arrow in Scan mode disallows skipping a disabled hyperlink

Copied from [VSO 20338011](https://microsoft.visualstudio.com/OS/_workitems/edit/20338011)

Feedback Details | Description
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Title | Narrator down arrow in Scan mode gets stuck in a disabled hyperlink
Description | - Run https://aka.ms/ke to install Kusto Explorer (Press Open when asked)- Switch to scan mode to read the dialog that comes up "Accept End User Licencing Agreement"- Beside the fact that the focus is a little off, when the focus is on the hyperlink "Your agreement", it got stuck. Narrator keeps saying "Your agreement" each time Down arrow is pressed.
User Impact | - When Narrator’s scan mode is used on a WPF RichTextBox that includes a disabled hyperlink the user would expect that after landing on the hyperlink arrow-key down should navigate to the text after the hyperlink, instead repeatedly pressing arrow-down key will always prompt narrator to announce the hyperlink. If the user simply lets Narrator finish reading the hyperlink’s text he or she can press arrow-down key and move to the next part of the text
Work Around | - If the user waits for Narrator to finish reading the hyperlink’s text, he or she can then press arrow-down key and Narrator’s focus will go to the text after as expected