Remove stripes from Settings

[karmatosed]

Is your feature request related to a problem? Please describe.
The stripes on settings make it harder to read and less fitting to the native experience. It also can cause issues with some interface elements. Here is what they look like.

Describe the solution you'd like
By removing the striping, this brings it more aligned to the options settings of the unified newer WP experience.

Describe alternatives you've considered
At later point exploring actually having the fuller modal would be good, but this starts that process by removing striping.
Removing striping on underline of menu could also be done.

[karmatosed]

Closing to move to iterations project.