Tooling: Update readme.txt files with updated stable tag in backport (#46034)

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/19552316460

Upstream-Ref: Automattic/jetpack@cc788a9

Author: tbradsha

readme.txt

@@ -4,7 +4,7 @@ Tags: performance, caching, wp-cache, wp-super-cache, cache
 Requires at least: 6.7
 Requires PHP: 7.2
 Tested up to: 6.9
-Stable tag: 2.0.0
+Stable tag: 3.0.3
 License: GPLv2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html