[IMP] test_lint: detect useless manifest content

Keep the manifests as light as possible, to easily see custom behavior/content.
Complete the work of previous commits cleaning the manifests content:

* 42bad1a6d2
* ef7005f524

and make sure this kind of cleanup commit is not necessary in the future
because it is now automatically verified by a dedicated test.

closes odoo/odoo#107735

Related: odoo/enterprise#34903
Signed-off-by: Julien Castiaux <juc@odoo.com>

odoo/modules/module.py

@@ -35,7 +35,7 @@ _DEFAULT_MANIFEST = {
     'demo_xml': [],
     'depends': [],
     'description': '',
-    'external_dependencies': [],
+    'external_dependencies': {},
     #icon: f'/{module}/static/description/icon.png',  # automatic
     'init_xml': [],
     'installable': True,