Update guidance site for changes to component sizing from `default` to `medium`

[ad9242]

Summary

Once changes for https://github.com/mi6/ic-ui-kit/issues/2072 are complete, the site should be reviewed to ensure the examples use medium instead of default

Following components have had size 'default' updated to 'medium':
Accordion Badge Button Checkbox Chip Date picker Empty state Loading indicator Page header Radio button Search bar Status tag Switch Text field Top navigation

[MI6-255]

Blocked by releasing v3

[ad9242]

there still seem to be some places where "default" is used, eg codePreview uses a "default" ic-button.