making "Don't ask me again" look more like a button under translation popup

[kjozwiak]

Description

As suggested by @johnnyryan, we should make the Don't ask me again string via the Translation modal appear as an actual button so users know they can click and disable the popup that appears every time Brave detects another language the the Google Translate extension isn't installed.

Steps to Reproduce

1. download and install brave
2. visit a page in another language/locale (example: https://www.spiegel.de)

Actual result:

Expected result:

Make the Don't ask me again appear as a button that's clickable rather than a string.

Reproduces how often:

100% reproducible using the above STR.

Brave version (brave://version info)

Brave | 1.7.78 Chromium: 80.0.3987.149 (Official Build) dev (64-bit)
-- | --
Revision | 5f4eb224680e5d7dca88504586e9fd951840cac6-refs/branch-heads/3987_137@{#16}
OS | macOS Version 10.15.3 (Build 19D76)

Version/Channel Information:

• Can you reproduce this issue with the current release? Yes
• 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:

CCing @rebron @johnnyryan @bsclifton