Revert "FEATURE: Allow theme tests to be run in production (#12815)" (#12840)

This reverts commit 7217dcb67a59f9c47d655455b60b4e1d8dc30f28.

https://meta.discourse.org/t/failed-to-bootstrap-due-to-out-of-memory-killer/188141/18?u=osama

Precompiling test_helper.js is so expensive that it can make bootstrap
fail on servers with limited resources (2GB RAM). We will find another
way that doesn't require much resources.

lib/theme_javascript_compiler.rb

@@ -151,6 +151,18 @@ class ThemeJavascriptCompiler
   class CompileError < StandardError
   end
 
+  def self.force_default_settings(content, theme)
+    settings_hash = {}
+    theme.settings.each do |setting|
+      settings_hash[setting.name] = setting.default
+    end
+    content.prepend <<~JS
+      (function() {
+        require("discourse/lib/theme-settings-store").registerSettings(#{theme.id}, #{settings_hash.to_json}, { force: true });
+      })();
+    JS
+  end
+
   attr_accessor :content
 
   def initialize(theme_id, theme_name)