Remove abortable source wrapper from response source

[wemeetagain]

There was a memory leak stemming from using abortable-iterator and neither fully draining the iterator nor aborting it.
abortable-iterator attaches an abort signal listener and only removes the listener after:

• the iterator is {done: true} OR
• the iterator is aborted

In our case, collectResponses breaks out of the iterator after maxResponses # of iterations.
So every request was leaking a listener.

For now, remove the abortable source wrapper until we can figure out a better solution.

[codeclimate]

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