refactor(@angular-devkit/build-optimizer): remove redundant webpack-sources dependency

The `webpack` package now exports the `Source` based classes directly.

Author: clydin

packages/angular_devkit/build_optimizer/BUILD.bazel

@@ -35,8 +35,6 @@ ts_library(
     module_root = "src/index.d.ts",
     deps = [
         "@npm//@types/node",
-        "@npm//@types/webpack",
-        "@npm//@types/webpack-sources",
         "@npm//source-map",
         "@npm//tslib",
         "@npm//typescript",

packages/angular_devkit/build_optimizer/package.json

@@ -12,8 +12,7 @@
     "loader-utils": "2.0.0",
     "source-map": "0.7.3",
     "tslib": "2.2.0",
-    "typescript": "4.2.4",
-    "webpack-sources": "2.2.0"
+    "typescript": "4.2.4"
   },
   "peerDependencies": {
     "webpack": "^5.30.0"

packages/angular_devkit/build_optimizer/src/build-optimizer/webpack-loader.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import { RawSourceMap } from 'source-map';
-import { SourceMapSource } from 'webpack-sources';
+import { sources } from 'webpack';
 const loaderUtils = require('loader-utils');
 
 import { buildOptimizer } from './build-optimizer';
@@ -72,7 +72,7 @@ export default function buildOptimizerLoader(
 
     if (previousSourceMap) {
       // Use http://sokra.github.io/source-map-visualization/ to validate sourcemaps make sense.
-      newSourceMap = new SourceMapSource(
+      newSourceMap = new sources.SourceMapSource(
         newContent,
         this.resourcePath,
         intermediateSourceMap,