Restore clone deep to not fail unit tests.

Author: l-lejman

packages/ckeditor5-core/src/context.ts

@@ -21,6 +21,8 @@ import { type Editor } from './editor/editor.js';
 import type { LoadedPlugins, PluginConstructor } from './plugin.js';
 import type { EditorConfig } from './editor/editorconfig.js';
 
+import { cloneDeep } from 'es-toolkit/compat';
+
 /**
  * Provides a common, higher-level environment for solutions that use multiple {@link module:core/editor/editor~Editor editors}
  * or plugins that work outside the editor. Use it instead of {@link module:core/editor/editor~Editor.create `Editor.create()`}
@@ -177,7 +179,7 @@ export class Context {
 			 * Since _translate is called often and has no access to the editor config, this is the better place
 			 * to check if translations will be taken from the global variable and update config.language.ui accordingly.
 			 */
-			const globalTranslations = global.window.CKEDITOR_TRANSLATIONS;
+			const globalTranslations = cloneDeep( global.window.CKEDITOR_TRANSLATIONS );
 			const uiLanguageFromConfig = typeof languageConfig === 'string' ? languageConfig : languageConfig.ui;
 			const hasMatchingTranslations = globalTranslations[ uiLanguageFromConfig! ];
 			const defaultGlobalTranslationsLanguage = Object.keys( globalTranslations )[ 0 ];