tweak style for gateway list item hover

[rustyjux]

Follows up on Tim's comment on #1179 - #1179 (review)

I'm wondering if we're able to style the Gateway display name with an underline based on the state of the parent to better match the styling of cards in the Gateways manager:

We think the hover background is rather dark but apparently that's the recommendation in the BC design tokens.

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🚀 Feature branch deployment: https://api-services-portal-feature-click-gateway-item.apps.silver.devops.gov.bc.ca

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🚀 Feature branch deployment: https://api-services-portal-feature-click-gateway-item.apps.silver.devops.gov.bc.ca

[timng-bcgov]

For reference, I'm following guidelines for the secondary button component from the Design System. The button doesn't toggle the label colour like we're doing here, but there are no concerns about contrast:

We still need to work on the keyboard focus state and semantic identification of the component (use a button or anchor element instead of a div).

[rustyjux]

@Elson9 waiting for review