Update migration that failed to run (#5946)

* Update migration that failed to run

* !fixup

priv/repo/migrations/20251211110619_goals_custom_props_default.exs

@@ -2,8 +2,23 @@ defmodule Plausible.Repo.Migrations.GoalsCustomPropsDefault do
   use Ecto.Migration
 
   def change do
+    drop(
+      unique_index(:goals, [:site_id, :event_name, :custom_props],
+        where: "event_name IS NOT NULL",
+        name: :goals_event_config_unique
+      )
+    )
+
     alter table(:goals) do
-      modify(:custom_props, :map, null: false, default: %{})
+      remove :custom_props
+      add :custom_props, :map, null: false, default: %{}
     end
+
+    create(
+      unique_index(:goals, [:site_id, :event_name, :custom_props],
+        where: "event_name IS NOT NULL",
+        name: :goals_event_config_unique
+      )
+    )
   end
 end