Revert "Ensure secret_key_base is set for all environments"

A better solution has been pushed to master.

This reverts commit 959cfce.

railties/test/isolation/abstract_unit.rb

@@ -137,7 +137,6 @@ def build_app(options = {})
       end
 
       add_to_config <<-RUBY
-        secrets.secret_key_base = "3b7cd727ee24e8444053437c36cc66c4"
         config.eager_load = false
         config.session_store :cookie_store, key: "_myapp_session"
         config.active_support.deprecation = :log
@@ -157,8 +156,8 @@ def make_basic_app
       require "action_view/railtie"
 
       app = Class.new(Rails::Application)
-      app.secrets.secret_key_base = "3b7cd727ee24e8444053437c36cc66c4"
       app.config.eager_load = false
+      app.secrets.secret_key_base = "3b7cd727ee24e8444053437c36cc66c4"
       app.config.session_store :cookie_store, key: "_myapp_session"
       app.config.active_support.deprecation = :log