Increase swipe to unlock height

Description

Increase the height of the 'swipe to unlock' control for ease of use while walking.

From current size (ic_swipe_unlock=32dp, plus 2 margins of 4dp) to an arbitrary higher value of 48dp plus same margins.

Motivation and Context

Please see #1501 (closed)

How Has This Been Tested?

Tested manually on Oneplus 6T in both portrait and landscape modes.

Screenshots / GIFs (if appropriate):

Before

After

Types of changes

• Enhancement (cosmetic / UI)

Checklist

• I have read the CONTRIBUTING section of the README document.