Remove remaining webpack references for building extensions

All extensions now should be fully ported over to use esbuild instead of webpack

extensions/json-language-features/server/.npmignore

@@ -6,5 +6,4 @@ test/
 tsconfig.json
 .gitignore
 package-lock.json
-extension.webpack.config.js
 vscode-json-languageserver-*.tgz