Remove test-prepare

test-prepare seems to be unneeded and potentially  harmful imo:

* the tests run fine without it, as `mix test` runs pending migrations
* reset also runs setup which runs the seeds which shouldn't
be in the test DB env unless we want to use them as fixtures but
then it'd probably better to separate dev seeds from test fixtures

So, I have it all running locally without ever running it 👍

README.md

@@ -128,12 +128,6 @@ mindwendel is built on top of:
   docker compose up --build -d
   ```
 
-- Ensure your database is running and reset your database
-
-  ```bash
-  docker compose exec app mix ecto.test.prepare
-  ```
-
 - Run the test
 
   ```bash

mix.exs

@@ -80,7 +80,6 @@ defmodule Mindwendel.MixProject do
     [
       "ecto.reset": ["ecto.drop", "ecto.setup"],
       "ecto.setup": ["ecto.create", "ecto.migrate", "run priv/repo/seeds.exs"],
-      "ecto.test.prepare": ["cmd MIX_ENV=test mix ecto.reset"],
       setup: ["deps.get", "ecto.setup", "cmd npm install --prefix assets"],
       test: ["ecto.create --quiet", "ecto.migrate --quiet", "test"],
       "assets.deploy": [