Modify journalist 2fa TOTP secret style

[DrGFreeman]

Status

Ready for review.

Description of Changes

Fixes #1598

Changes proposed in this pull request:

Change styling of journalist 2FA TOTP secret text:

• Change background color to light grey
• Remove border
• Increase lateral and vertical padding
• Use monospace font
• Increase font size
• Use bold font weight

Testing

How should the reviewer test this PR?
Write out any special testing steps here.

1. Run make dev.
2. In journalist interface, create a new user.
3. On the /admin/2fa page, check the style of the TOTP secret text. The expected style is shown in the screenshot below.

Deployment

Any special considerations for deployment? Consider both:

1. Upgrading existing production instances.
2. New installs.

Checklist

If you made changes to the server application code:

• Linting (make lint) and tests (make test) pass in the development container

If you made changes to securedrop-admin:

• Linting and tests (make -C admin test) pass in the admin development container

If you made changes to the system configuration:

• Configuration tests pass

If you made non-trivial code changes:

• I have written a test plan and validated it for this PR

If you made changes to documentation:

• Doc linting (make docs-lint) passed locally

If you added or updated a code dependency:

Choose one of the following:

• I have performed a diff review and pasted the contents to the packaging wiki
• I would like someone else to do the diff review

[DrGFreeman]

Expected style:

[kushaldas]

The UI looks good and same as in the screenshot.