Fix Sass deprecation on mix function (passing a number without unit)

[paulrobertlloyd]

Description

SASS is showing the following deprecation warning. Example:

Deprecation Warning: $weight: Passing a number without unit % (50%*%) is deprecated.

To preserve current behavior: calc($weight / 1% / 1% * 1%)

More info: https://sass-lang.com/d/function-units

   ╷
72 │   @return mix(black, $color, $percentage * 1%);
   │           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   ╵
    packages/core/settings/_colours.scss 72:11  shade()
    packages/core/settings/_colours.scss 90:29  @import
    packages/core/settings/_all.scss 6:9        @import
    packages/core/all.scss 6:9                  @import
    packages/nhsuk.scss 2:9                     root stylesheet

As we are always passing a percentage to the tint and shade functions, we don’t need to multiple the incoming value by 1%. This resolves this warning.

Checklist

• Tested against our testing policy (Resolution, Browser & Accessibility)
• Follows our coding standards and style guide
• CHANGELOG entry

[frankieroberto]

Ah good stuff, this has been annoying me too.