Update 'Tested up to' version to WP 5.3 (#1282)

Author: Aljullu

readme.txt

@@ -2,7 +2,7 @@
 Contributors: automattic, claudiulodro, tiagonoronha, jameskoster, ryelle, levinmedia, aljullu, mikejolley, nerrad, joshuawold
 Tags: gutenberg, woocommerce, woo commerce, products, blocks, woocommerce blocks
 Requires at least: 5.0
-Tested up to: 5.2
+Tested up to: 5.3
 Requires PHP: 5.6
 Stable tag: 2.6.0-dev
 License: GPLv3