Update from drewm/mailchimp-api v2.5.3 to v2.5.4

[benlk]

https://github.com/drewm/mailchimp-api/releases/tag/v2.5.4

link-roundups/composer.lock

Lines 9 to 16 in be0f2a9

	{
	"name": "drewm/mailchimp-api",
	"version": "v2.5.3",
	"source": {
	"type": "git",
	"url": "https://github.com/drewm/mailchimp-api.git",
	"reference": "a6519cafba509e754e748d93f3532ad7f3aa515a"
	},