[FIX] fix manifest

Author: thjo-odoo

addons/mass_mailing_egg/__manifest__.py

@@ -52,7 +52,6 @@
         'web.assets_backend': [
             'mass_mailing_egg/static/src/fields/**/*',
             'mass_mailing_egg/static/src/themes/**/*',
-            'mass_mailing_egg/static/src/mobile_preview_dialog/**/*',
             'mass_mailing_egg/static/src/iframe/**/*',
         ],
         'web.assets_unit_tests': [