fix(typography): deprecation warning in latest sass version (#14673)

* Updates to the latest `node-sass` version.
* Fixes the build not using the `node-sass` version from the package.json.
* Fixes a deprecation warning from the latest SASS version when the consumer has configured a non-string `font-family` (e.g. `Helvetica Neue`).

Fixes #14636.

tools/package-tools/gulp/build-scss-pipeline.ts

@@ -4,6 +4,7 @@ import {buildConfig} from '../build-config';
 
 // These imports lack of type definitions.
 const gulpSass = require('gulp-sass');
+const nodeSass = require('node-sass');
 const gulpIf = require('gulp-if');
 const gulpCleanCss = require('gulp-clean-css');
 
@@ -11,6 +12,9 @@ const sassIncludePaths = [
   join(buildConfig.projectDir, 'node_modules/')
 ];
 
+// Set the compiler to our version of `node-sass`, rather than the one that `gulp-sass` depends on.
+gulpSass.compiler = nodeSass;
+
 /** Create a gulp task that builds SCSS files. */
 export function buildScssPipeline(sourceDir: string, minifyOutput = false) {
   return src(join(sourceDir, '**/*.scss'))