Switch flight CSV variables

[Seth-Rothschild]

Previous PR used the larger CSV when the demo=True option was selected in load_flight. This fixes that.

[codecov-io]

Codecov Report

Merging #228 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #228      +/-   ##
==========================================
- Coverage   93.58%   93.56%   -0.02%     
==========================================
  Files          71       71              
  Lines        7727     7727              
==========================================
- Hits         7231     7230       -1     
- Misses        496      497       +1

Impacted Files	Coverage Δ
featuretools/demo/flight.py	88.63% <100%> (ø)	⬆️
featuretools/utils/gen_utils.py	64.44% <0%> (-2.23%)	⬇️

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[kmax12]

Looks good. Merging