Connection: fix the connected plugins option on multisites (#39355)

Recent optimizations of the connected plugin options update/sync exposed an issue in the original implementation, making the "active connected plugins" option always empty on multisites.
Here we fix that problem.

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/10817836631

Upstream-Ref: Automattic/jetpack@11ebad6

composer.json

@@ -5,7 +5,7 @@
 	"license": "GPL-2.0-or-later",
 	"require": {
 		"php": ">=7.0",
-		"automattic/jetpack-connection": "^4.0.2",
+		"automattic/jetpack-connection": "^4.0.3-alpha",
 		"automattic/jetpack-sync": "^3.13.0-alpha"
 	},
 	"require-dev": {