Update natural gas units

[elenya-grant]

Update natural gas units

The natural gas model uses units of MMBtu for natural gas in, but it should be in MMBtu/h.

The places this needs to be updated:

• h2integrate/converters/natural_gas/natural_gas_cc_ct.py: NaturalGasPerformanceModel in setup(), update natural_gas_consumed and natural_gas_in to have units of MMBtu/h instead of MMBtu
• update the natural gas feedstock units in tech configs for example 16, 21, 23 and in h2integrate/core/test/test_feedstocks.py
• update units in h2integrate/transporters/pipe.py if "transport_item=="natural_gas"

[elenya-grant]

Resolved in PR #523