update version number in readme

Author: Kristófer R

readme.txt

@@ -4,7 +4,7 @@ Tags: credit card, stripe, apple pay, payment request, google pay, sepa, sofort,
 Requires at least: 5.7
 Tested up to: 6.0
 Requires PHP: 7.0
-Stable tag: 6.9.0
+Stable tag: 7.0.0
 License: GPLv3
 License URI: https://www.gnu.org/licenses/gpl-3.0.html
 Attributions: thorsten-stripe