fix(modules-sdk): medusa app load legacy modules (#5115)

* fix: default module path

* fix: allow legacy modules to be loaded by MedusaApp

* changeset

---------

Co-authored-by: Adrien de Peretti <adrien.deperetti@gmail.com>

.changeset/lucky-bulldogs-juggle.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/modules-sdk": patch
+---
+
+Allow MedusaApp load legacy modules

packages/modules-sdk/src/loaders/register-modules.ts

@@ -73,12 +73,6 @@ export const registerMedusaModule = (
     throw new Error(`Module: ${moduleKey} is not defined.`)
   }
 
-  if (modDefinition.isLegacy) {
-    throw new Error(
-      `Module: ${moduleKey} is a legacy module. Please use registerModules instead.`
-    )
-  }
-
   if (
     isObject(moduleDeclaration) &&
     moduleDeclaration?.scope === MODULE_SCOPE.EXTERNAL