Increasing Astronomer's sponsorship of Airflow CI by 4x

[Ash Berlin-Taylor]

Hi everyone,

I have a little bit of good news: I've spoken to the finance people at 
Astronomer and have just had sign-off to increase our sponsorship of 
Airflow's CI infrastructure by  4x the current amount.

Hopefully this should mean reduced queue times for everyone (though the 
biggest impact will be felt by committers!) at quieter periods many of 
the Test jobs will be able to run in parallel!

Cheers,
Ash