JITMs: Fix styling to work better with a popular plugin, take 2

[jeherve]

fixes #9221

Changes proposed in this Pull Request:

Another take on #10539, that had to be reverted.

Testing instructions:

1. Turn on Hello Dolly on a site with no plan and akismet inactive
2. View the comments page
3. See a jitm that doesn't collide with the hello dolly text
4. Turn off Hello Dolly
5. Make sure the JITMs still look good.

Proposed changelog entry for your changes:

• Notices: fix styling to work better with the Hello Dolly plugin

[jetpackbot]

Thank you for the great PR description!

When this PR is ready for review, please apply the [Status] Needs Review label. If you are an a11n, please have someone from your team review the code if possible. The Jetpack team will also review this PR and merge it to be included in the next Jetpack release.

Scheduled Jetpack release: January 10, 2019.
Scheduled code freeze: January 3, 2019

Generated by 🚫 dangerJS

[jeherve]

closing. Replaced by #10840