fix(dev-scripts): Don't use alias when resolving blockly

PR google#226 addedd a resolve.alias for blockly to webpack.config.js.
It is not entirely clear what the purpose of this was at the
time, but it has the effect of treating imports of submodules
(e.g. 'blockly/core') as if they were direct imports (e.g. of
'./node_modules/blockly/core.js'), causing webpack to ignore
the blockly package's package.json file.

This causes plugins to fail to build due to the introduction
of an exports stanza in that file (and other related changes)
in google/blockly#7822.

plugins/dev-scripts/config/webpack.config.js

@@ -74,9 +74,6 @@ module.exports = (env) => {
       clean: true,
     },
     resolve: {
-      alias: {
-        'blockly': resolveApp('node_modules/blockly'),
-      },
       extensions: ['.ts', '.js'].filter(
         (ext) => isTypescript || !ext.includes('ts'),
       ),