Sync warning message formatting - follow up to 4132

[LaurenWags]

Description

Follow up to #4132

Issue above states that both code words and QR code screens should display message that the sync key is sensitive with some degree of bolding to the message (see description and #4132 (comment)). Message currently blends in to the rest of the text on the modal.

Steps to Reproduce

1. Navigate to brave://sync
2. Select Start a new Sync Chain
3. Select 'Computer', you will see added message as dictated in Sync should show warning not to share the code with anyone #4132 (comment) except for bolding. QR code screen should display this message as well, but currently does not (logged as Sync QR code screen should show same warning message as code words screen - follow up to 4132 #4491)

Actual result:

Expected result:

Expecting bold text per #4132 (comment). If this is no longer the expected result, please close this issue.

Reproduces how often:

easily

Brave version (brave://version info)

Brave	0.65.95 Chromium: 74.0.3729.131 (Official Build) beta(64-bit)
Revision	518a41c1fa7ce1c8bb5e22346e82e42b4d76a96f-refs/branch-heads/3729@{#954}
OS	Mac OS X

Version/Channel Information:

• Can you reproduce this issue with the current release? n/a
• Can you reproduce this issue with the beta channel? yes
• Can you reproduce this issue with the dev channel? yes
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Does the issue resolve itself when disabling Brave Rewards? n/a
• Is the issue reproducible on the latest version of Chrome? n/a

Miscellaneous Information:

[LaurenWags]

cc @diracdeltas as original issue had security tag.

[rebron]

Good catch @LaurenWags We should have the "Treat this code like a password" in bold.