update Sync Chain QR Code dialog text

[rebron]

Description

Replace: On your mobile device, navigate to Brave Sync in the Settings panel and click the button "Scan Sync code" Use your camera to scan the QR Code below.

With: "On your mobile device, navigate to Brave Sync in the Settings panel and click the button "Scan or enter sync code". Use your camera to scan the QR Code below."

If adding "or enter" bumps text to a third line, can skip this edit change and can keep "Scan Sync code"

Note the missing period in between sentences. Make sure to add with the corrected text.

[btlechowski]

Verification passed on

Brave	0.59.25 Chromium: 72.0.3626.53 (Official Build) beta (64-bit)
Revision	98434e6cd182d68ce396daa92e9c6310422e6763-refs/branch-heads/3626@{#620}
OS	Windows 7

Verified the dialog in Start a New Sync Chain, View Sync Code, and Add New Device

Verification passed on

Brave	0.59.25 Chromium: 72.0.3626.53 (Official Build) beta (64-bit)
Revision	98434e6cd182d68ce396daa92e9c6310422e6763-refs/branch-heads/3626@{#620}
OS	Linux

Verified with

Brave	0.59.25 Chromium: 72.0.3626.53 (Official Build) beta(64-bit)
Revision	98434e6cd182d68ce396daa92e9c6310422e6763-refs/branch-heads/3626@{#620}
OS	Mac OS X