fix(build): remove stale node: builtin externals breaking consumer webpack builds

The externals block for 'node:fs'/'node:path'/etc. became dead weight when
originally added, but the webpack 5.108.4 bump now canonicalizes bare builtin
requires to the node: form, matching it. That flips these modules from being
polyfilled by node-polyfill-webpack-plugin to leaking as unresolved literal
requires in the published bundle.

webpack.config.js

@@ -27,15 +27,6 @@ const browserConfig = {
     index: './src/index.ts',
     minified_sas9: './src/minified/sas9/index.ts'
   },
-  externals: {
-    'node:fs': 'node:fs',
-    'node:fs/promises': 'node:fs/promises',
-    'node:path': 'node:path',
-    'node:stream': 'node:stream',
-    'node:url': 'node:url',
-    'node:events': 'node:events',
-    'node:string_decoder': 'node:string_decoder'
-  },
   output: {
     filename: '[name].js',
     path: path.resolve(__dirname, 'build'),