Revert "Avoid returning an unused column."

[clokep]

Reverts #13933.

Turns out this is used, but in a confusing spot further down in the code:

synapse/synapse/storage/databases/main/event_push_actions.py

Lines 1124 to 1127 in 7766bd5

	# If we pulled out a limited number of rows we only update the
	# position to the last receipt we processed, so we continue
	# processing the rest next iteration.
	upper_limit = rows[-1][0]

[DMRobertson]

Arg, sorry.

I suppose we wouldn't have been able to catch this without castint the type of rows. Frustrating.

[DMRobertson]

(Did CI not catch this on #13933?)

[clokep]

(Did CI not catch this on #13933?)

It did not, I think none of the tests hit a 100 receipt limit.