fix: Declare the SCSS license headers with line comments

[TrevorBurnham]

Description

Part of cloudscape-design/components#4905.

Sass copies loud comments into the compiled CSS, so a partial's license header is emitted once per stylesheet that @uses it. Both SCSS files in this repo are consumed exactly that way: postbuild copies them into lib, and package.json exports them as the sass/style entry points that @cloudscape-design/components and its siblings @use.

Declaring the header with line comments keeps the notice in the shipped source while keeping it out of consumers' compiled output.

Measured by building cloudscape-design/components against this change: 16.5 KB of duplicated comments removed from its 1770 KB of published CSS, and the median goes from two license blocks per stylesheet down to one. I diffed all 229 compiled stylesheets before and after; the only differences are the removed comments and the generated scoped-name hashes, which embed a content hash and a line number.

Two notes on why this is safe:

• Neither file is compiled to CSS in this repo. npm run build only copies them.
• Both are already pure Sass, using @mixin, @use 'sass:map', and // comments throughout their bodies. Nothing can consume them as plain CSS today, so line comments add no new constraint. The block header was the only comment in either file not already using //.

This is independent of the two related PRs and can land in any order:

• feat: Add commentType option to the license-headers stylelint rule build-tools#75 adds a commentType option to the license-headers stylelint rule. This repo has no stylelint config, so it does not need that rule.
• fix: Stop repeating the license header in every compiled stylesheet components#4906 does the same conversion for that repo's 89 partials.

How has this been tested?

Built cloudscape-design/components against the patched files and compared all 229 compiled stylesheets, as described above.