I noticed that DonationInterface's vendor has polyfill-php54, polyfill-php55, polyfill-ctype and polyfill-mbstring

You definitely don't need the first two (even on MW 1.31 you need newer PHP), and you almost certainly don't need the other two

If you add something like the below to composer.json:

	"replace": {
		"symfony/polyfill-ctype": "1.99",
		"symfony/polyfill-mbstring": "1.99",
		"symfony/polyfill-php54": "1.99"
		"symfony/polyfill-php55": "1.99"
	},

And then run composer update --no-dev, it'll remove them