Both `<aio-contributor-list>` and `<aio-resource-list>` contain
`.group-buttons` elements. Previously, global styles for
`.group-buttons` were defined in `_contributor.scss` (i.e. the styles
from `_contributor.scss` were also applied to `.group-buttons` in
`<aio-resource-list>`). Also, `_contributor.scss` and `_resources.scss`
defined some duplicate styles for `.group-buttons`.
This commit moves the `.group-buttons` styles to `_buttons.scss`, which
contains common button-related styles.
PR Close#40704
6357532c59