Connection: initialize assets in wp-admin only (#39604)

Only initialize Connection assets in the admin area.

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/11146707292

Upstream-Ref: Automattic/jetpack@43bb3b3

composer.json

@@ -5,7 +5,7 @@
 	"license": "GPL-2.0-or-later",
 	"require": {
 		"php": ">=7.0",
-		"automattic/jetpack-connection": "^5.1.1"
+		"automattic/jetpack-connection": "^5.1.2-alpha"
 	},
 	"require-dev": {
 		"yoast/phpunit-polyfills": "^1.1.1",