fix(dynamo): handle dyamo crash

[rudiejd]

Summary of changes

Asana Ticket: N/A

Handle dynamo crash when scanning records

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[jzimbel-mbta]

nit:
I don't really like that neither this nor any of the other calls to do_paginated_query handle its potential error tuple return value, but it doesn't make a huge difference--the tuple will be surfaced when Enum.flat_map raises on it:

** (Protocol.UndefinedError) protocol Enumerable not implemented for {:error, "foo"} of type Tuple
<stacktrace snipped>

so I guess it's fine.
Would prefer to have do_paginated_query just raise directly if all of the call sites will end up raising anyway.