Remove the envify command

Instead of using `kamal envify` to generate the .env file, we now assume
that it will be in place for us.

Options in place of `kamal envify`:
1. Pre-generate the .env file
2. Create the env file in the `.pre-init` hook
3. Log into a secret store/check you are logged in in the pre-init hook
   Then use .dotenv command and variable substitution to interpolate the
   secrets.

test/integration/lock_test.rb

@@ -2,8 +2,6 @@ require_relative "integration_test"
 
 class LockTest < IntegrationTest
   test "acquire, release, status" do
-    kamal :envify
-
     kamal :lock, :acquire, "-m 'Integration Tests'"
 
     status = kamal :lock, :status, capture: true