✅(backend) fix translations in tests

Some translation have changed, the tests related to this string must be
updated accordingly.

src/backend/core/tests/documents/test_api_document_invitations.py

@@ -457,7 +457,7 @@ def test_api_document_invitations_create_email_from_senders_language():
     assert email.to == ["guest@example.com"]
 
     email_content = " ".join(email.body.split())
-    assert f"{user.full_name} a partagé un document avec vous!" in email_content
+    assert f"{user.full_name} a partagé un document avec vous !" in email_content
     assert (
         "Docs, votre nouvel outil incontournable pour organiser, partager et collaborer "
         "sur vos documents en équipe." in email_content

src/backend/core/tests/documents/test_api_documents_mention.py

@@ -366,10 +366,10 @@ def test_api_documents_mention_thread():
     Mentions can be attached to a comment thread of the document, in which case
     the email notification mentions the comment.
     """
-    user = factories.UserFactory(full_name="Mentioning User")
+    user = factories.UserFactory(full_name="Mentioning User", language="en-us")
     document = factories.DocumentFactory(title="My doc")
     factories.UserDocumentAccessFactory(document=document, user=user, role="commenter")
-    mentioned_user = factories.UserFactory()
+    mentioned_user = factories.UserFactory(language="en-us")
     factories.UserDocumentAccessFactory(
         document=document, user=mentioned_user, role="commenter"
     )