Patterns: use existing download function for JSON downloads to fix no…

…n-ASCII encoding (#55912)

* downloadjs has a bug where it cannot decode non-ASCII characters.
Gutenberg's reusable blocks code has an existing download function that we can use for JSON. This commit removes the downloadjs dependency and copies over the reusable blocks download function.

* Added comment to explain duplicate

* Remove IE11-specific code.

packages/edit-site/src/components/page-patterns/grid-item.js

@@ -2,7 +2,6 @@
  * External dependencies
  */
 import classnames from 'classnames';
-import downloadjs from 'downloadjs';
 import { paramCase as kebabCase } from 'change-case';
 
 /**
@@ -52,6 +51,25 @@ import { store as editSiteStore } from '../../store';
 import { useLink } from '../routes/link';
 import { unlock } from '../../lock-unlock';
 
+/**
+ * Downloads a file.
+ * Also used in packages/list-reusable-blocks/src/utils/file.js.
+ *
+ * @param {string} fileName    File Name.
+ * @param {string} content     File Content.
+ * @param {string} contentType File mime type.
+ */
+function download( fileName, content, contentType ) {
+	const file = new window.Blob( [ content ], { type: contentType } );
+	const a = document.createElement( 'a' );
+	a.href = URL.createObjectURL( file );
+	a.download = fileName;
+	a.style.display = 'none';
+	document.body.appendChild( a );
+	a.click();
+	document.body.removeChild( a );
+}
+
 const { useGlobalStyle } = unlock( blockEditorPrivateApis );
 
 const templatePartIcons = { header, footer, uncategorized };
@@ -118,9 +136,9 @@ function GridItem( { categoryId, item, ...props } ) {
 			syncStatus: item.patternBlock.wp_pattern_sync_status,
 		};
 
-		return downloadjs(
-			JSON.stringify( json, null, 2 ),
+		return download(
 			`${ kebabCase( item.title || item.name ) }.json`,
+			JSON.stringify( json, null, 2 ),
 			'application/json'
 		);
 	};