Remove unused property and mock

[chrismccluskey]

Changes proposed in this Pull Request

• Removes a property and a mock which were are no longer in use.

Testing instructions

• Automated tests.

Mentions # 549-gh-automattic/gold

[github-actions]

Package	Line Rate	Complexity	Health
inc/abuse-decisions-actions.php	0%	22	❌
inc/abuse-decisions.php	0%	12	❌
inc/class-sift-event-types.php	100%	4	✔
inc/payment-gateway.php	100%	5	✔
inc/payment-gateways/index.php	0%	0	❌
inc/payment-gateways/lib/stripe.php	63%	77	➖
inc/payment-gateways/load.php	0%	0	❌
inc/payment-gateways/paypal.php	0%	0	❌
inc/payment-gateways/stripe.php	23%	17	❌
inc/payment-gateways/transact.php	100%	0	✔
inc/payment-gateways/woocommerce-payments.php	32%	8	❌
inc/payment-method.php	97%	31	✔
inc/payment-type.php	83%	3	✔
inc/rest-api-webhooks.php	0%	5	❌
inc/sift-object-validator.php	87%	134	✔
inc/sift-order.php	96%	6	✔
inc/sift-property.php	100%	3	✔
inc/tracking-js.php	0%	4	❌
inc/verification-status.php	50%	3	➖
inc/wc-settings-tab.php	0%	24	❌
inc/woocommerce-actions.php	71%	112	➖
index.php	0%	0	❌
sift-for-woocommerce.php	0%	9	❌
Summary	54% (964 / 1769)	479	➖