Update migrations

priv/repo/migrations/20250607124601_create_activities.exs

@@ -1,18 +0,0 @@
-defmodule Nulla.Repo.Migrations.CreateActivities do
-  use Ecto.Migration
-
-  def change do
-    create table(:activities, primary_key: false) do
-      add :id, :bigint, primary_key: true
-      add :type, :string, null: false
-      add :actor, :string, null: false
-      add :object, :map, null: false
-      add :to, {:array, :string}, default: []
-
-      timestamps()
-    end
-
-    create index(:activities, [:actor])
-    create index(:activities, [:type])
-  end
-end