Remove horizontal padding within primary nav

[frankieroberto]

This removes the horizontal padding within the items in the primary navigation.

Whilst the horizontal padding does increase the target area, it also leads to the border-bottom on the first item extending into the margin of the page, which arguably looks a bit odd.

The draft One Login service header does not add horizontal padding, and neither does many of the service using this pattern (for example, Apply for teacher training) or the version of the pattern in the MOJ design system.

However the primary navigation bar on the Design System website itself does add horizontal padding.

An in-between option might be to have the padding for the increased target area, but to keep the border on the bottom of the active item to the width of the text.

However, given the height of the navigation bar, and the likely width of each item (which depends on the text), I think the target area size could already be considered sufficient?

Screenshots

Before

After

[paulrobertlloyd]

Looks good to me. The padding is such as it is because it follows the design of the Design System website, but given that the One Login service header has diverged, and consensus has formed around the alternative design, I think we should use that.

Feel free to merge after fixing the linting error.

[paulrobertlloyd]

This line is tripping up the linter.

Also… oooh, new textboxes on GitHub!