Backport jetpack 15.5-beta changes (#46893)

* Changelog and readme.txt edits.

* Amend readme.txt

* Update stable tag in readme.txt

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/21618989026

Upstream-Ref: Automattic/jetpack@ad261bf

Author: manzoorwanijk

composer.json

@@ -5,7 +5,7 @@
 	"license": "GPL-2.0-or-later",
 	"require-dev": {
 		"yoast/phpunit-polyfills": "^4.0.0",
-		"automattic/jetpack-changelogger": "^6.0.13-alpha",
+		"automattic/jetpack-changelogger": "^6.0.13",
 		"automattic/phpunit-select-config": "^1.0.3"
 	},
 	"autoload": {