[Tabs] A white flickering line is displayed at the top and bottom borders of the thumbnails

[Softvision-RemusDranca]

[Notes]:

• The white line is more visible when the thumbnails are selected and scrolled but they are slightly visible in normal view also, cutting the borders of the thumbnails.

[Affected Versions]:

• Firefox Reality 9 RC3 (18aba8b).

[Affected Platforms]:

• Pico Neo 2 - Android - 8.1.0
• Oculus Quest - Android 7.1.1
• HTC Vive Focus Plus - Android 7.1.2

[Prerequisites]:

• The headset is turned on and the app is opened.
• Have multiple tabs opened.

[Steps to reproduce]:

1. Click the View Tabs button.
2. Click the "Select" button.
3. Click the "Select All" button.
4. Scroll the page and observe the thumbnails.

[Expected results]:

• They are displayed correctly.

[Actual results]:

• A white flickering line is displayed at the top and bottom borders.

[Additional Notes]:

• Attached is a screen recording of the issue: link.

[bluemarvin]

@daron-walters Will you have a PR ready for code freeze next week or should we move this to v12?

[daron-walters]

move to v12