[data] Remove TestStreamOutputBackpressurePolicy.test_e2e_backpressure

[raulchen]

Why are these changes needed?

This test is flaky. The purpose of this test is to check that the producer will pause stop producing blocks after block 2 is generated and before block 0 is taken by the consumer. However it's hard to collect the timestamps for some events that happen in Data and Core internal. E.g., the time when an object is taken at the streaming generator level. We used the consumer task timestamp as an approximation. But the test is still flaky on some slow machines where the task can take long time to get started after being scheduled.

Remove this flaky test as we already have another e2e backpressure test test_large_e2e_backpressure, which will check the amount of spilling data.

Related issue number

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[aslonnie]

ping-a-ling?