Remove outdated `wcpay_transactions_download` tracking events. (#7627) #21008

Job	Run time
WP - nightly \| WC - latest \| wcpay - merchant	11m 9s
Generate the matrix for subscriptions-tests dynamically	1s
WP - nightly \| WC - latest \| wcpay - shopper	11m 40s
WP - nightly \| WC - latest \| subscriptions - merchant	7m 18s
WP - nightly \| WC - latest \| subscriptions - shopper	6m 33s
WC - 7.7.0 \| wcpay - merchant	10m 59s
WC - 7.7.0 \| wcpay - shopper	14m 29s
WC - 7.7.0 \| subscriptions - merchant	4m 39s
WC - 7.7.0 \| subscriptions - shopper	9m 33s
WC - latest \| wcpay - merchant	16m 6s
WC - latest \| wcpay - shopper	16m 47s
WC - latest \| subscriptions - merchant	6m 30s
WC - latest \| subscriptions - shopper	6m 36s
	2h 2m 20s

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