#25707 - Fixed flakiness in stata write test
This is my first contribution, so please be gentle.
 
For future reference, this error occurs when the two files are written in different minutes. I couldn't break the comparison by feeding the test datetime objects that only changed the seconds, so I assume only the date, hours, and minutes, are encoded. 

Anyway, we can't pass `False` as a keyword argument for `time_stamp`. It defaults to `None`, which internally uses the current timestamp, but otherwise expects a datetime.

For testing purposes, it suffice to pass the same arbitrary timestamp as a keyword. That way it encodes the same timestamp into each file, regardless of when the test runs and how long it takes.

Instead of `False`, we could use a keyword argument like this: `{'time_stamp': pd.to_datetime('2019-01-01 00:00')}`
