changelogger: Actually update tests to use addCommand() (#46149)

PR #46126 left the call to `add()` with a Phan suppression. This changes
it to use an `is_callable()` check to determine the correct method to
call, and adds a `@todo` comment flagging it for future cleanup.

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/19862663152

Upstream-Ref: Automattic/jetpack@6fa03ba

Author: anomiex

composer.json

@@ -16,7 +16,7 @@
 	},
 	"require-dev": {
 		"yoast/phpunit-polyfills": "^4.0.0",
-		"automattic/jetpack-changelogger": "^6.0.10",
+		"automattic/jetpack-changelogger": "^6.0.11-alpha",
 		"automattic/jetpack-test-environment": "@dev",
 		"automattic/phpunit-select-config": "^1.0.3"
 	},