Update copy for new app provisioning

- change flashed message for adding members
- use the correct helper text for the app name input
- a few other updates to text in translations

atst/routes/applications/settings.py

@@ -183,11 +183,7 @@ def handle_create_member(application_id, form_data):
                 token=invite.token,
             )
 
-            flash(
-                "new_application_member",
-                user_name=invite.user_name,
-                application_name=application.name,
-            )
+            flash("new_application_member", user_name=invite.first_name)
 
         except AlreadyExistsError:
             return render_template(