Changing capability type without altering plugin

you can achieve this one by adding one plugin “user Role Manager”

Link for It https://wordpress.org/plugins/user-role-editor

Steps

  1. Install user Role Manager First. and activate it.
  2. Create custom role or Edit Subscriber default role to set that page
    edit permission
  3. Set default role in setting as custom role if custom role created.
  4. Its Done.