Fix Dataframe header type to allow integer values

[abidlabs]

Tiny fix, but because of this issue demo/dataframe_streaming/run.py wasn't failing at startup, which in turn was causing all of our functional tests to pass spuriously.

e.g. see #10577 where all of the functional tests pass even though the tests do not run.

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Fix Dataframe header type to allow integer values

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[abidlabs]

Functional tests are failing, which I'm able to repro locally. Will look into tomorrow and fix before merging this in