docs: remove imports from src in medusa-config.js (#8132)

Importing from `src` in `medusa-config.js` works in development, but would cause an error when running `build`/in production.

This removes from the docs all snippets that imports from the `src` directory. However, we should figure out a better way to handle re-using the module's name.

www/apps/book/app/advanced-development/modules/options/page.mdx

@@ -23,13 +23,10 @@ To pass options to a module, add an `options` property to the module’s configu
 For example:
 
 ```js title="medusa-config.js"
-import { HELLO_MODULE } from "./src/modules/hello"
-// ...
-
 module.exports = defineConfig({
   // ...
   modules: {
-    [HELLO_MODULE]: {
+    helloModuleService: {
       resolve: "./modules/hello",
       options: {
         capitalize: true,