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.

spec/models/theme_spec.rb

@@ -865,41 +865,4 @@ HTML
     end
   end
 
-  describe "#baked_js_tests_with_digest" do
-    before do
-      ThemeField.create!(
-        theme_id: theme.id,
-        target_id: Theme.targets[:settings],
-        name: "yaml",
-        value: "some_number: 1"
-      )
-      theme.set_field(
-        target: :tests_js,
-        type: :js,
-        name: "acceptance/some-test.js",
-        value: "assert.ok(true);"
-      )
-      theme.save!
-    end
-
-    it 'returns nil for content and digest if theme does not have tests' do
-      ThemeField.destroy_all
-      expect(theme.baked_js_tests_with_digest).to eq([nil, nil])
-    end
-
-    it 'digest does not change when settings are changed' do
-      content, digest = theme.baked_js_tests_with_digest
-      expect(content).to be_present
-      expect(digest).to be_present
-      expect(content).to include("assert.ok(true);")
-
-      theme.update_setting(:some_number, 55)
-      theme.save!
-      expect(theme.build_settings_hash[:some_number]).to eq(55)
-
-      new_content, new_digest = theme.baked_js_tests_with_digest
-      expect(new_content).to eq(content)
-      expect(new_digest).to eq(digest)
-    end
-  end
 end