Remove temporary base.css import.

Closes #3473131

splitcss.js

@@ -13,8 +13,6 @@ const fullComponentDir = isSubtheme ? './components_combined/' : componentDir;
 const baseOutDir = './dist/';
 const cssHeader = '/**\n * This file was automatically generated. Please run `npm run dist` to update.\n */\n\n';
 const cssFooter = '\nimg \{\n  display: block;\n  max-width: 100%;\n  height: auto;\n\}\n\n';
-// @todo Once XB pulls in libraries, this can be removed.
-const baseImport = isSubtheme ? '\n@import url("../../../../dist/base.css")\;\n\n' : '\n@import url("../../../dist/base.css")\;\n\n';
 
 // Get Mixin file paths.
 const mixins = globSync(`00-base/mixins/**/*.scss`, { cwd: fullComponentDir });
@@ -65,7 +63,5 @@ fileList.forEach(filePath => {
   const result = sass.compileString(styleData, { loadPaths: [fullComponentDir] });
 
   // Write to directory.
-  // @todo Once XB handles libraries, remove baseImport.
-  fs.writeFileSync(`${componentDir}/${styleDir}/${styleName}.css`, cssHeader + baseImport + result.css);
-  //fs.writeFileSync(`${componentDir}/${styleDir}/${styleName}.css`, cssHeader + result.css);
+  fs.writeFileSync(`${componentDir}/${styleDir}/${styleName}.css`, cssHeader + result.css);
 });