Bug#1044076: influxdb-python and pandas 2.1

[Rebecca N. Palmer]

Some looking through the code suggests that the precision is user-set 
and hence constant within a single query, and hence that this fix is OK, 
but I'm not entirely certain of that.

There are ways to make pandas 2.x accept mixed time format, but I think 
they're 2.x _only_ and/or slow.