Update average intensity with latest data

[fershad]

This PR updates the average Grid Intensity data in CO2.js with the latest available data from Ember. It changes a few things:

• 🤖 Fetches data from Ember's data API, rather than relying on us having to manually download & manipulate a CSV file.
• 📆 It returns the latest available data for all countries/regions in the Ember dataset rather than the most recent calendar year.
  • 💡 This means we now have average availability data for 221 countries
  • ⚠️ Some countries don't have emissions data for the last few years (Reunion for example last reported in 2011 - in this case, we return the 2011 data)
• 🤖 Removes the year suffix on the filename. This paves the way for automating the update process, so that it can be run periodically through a Github action.

[fershad]

I've also fixed an error with the marginal intensity code that was causing the npm run intensity-data command to fail.

[fershad]

LOL of course this would cause tests to fail, since the average intensity data used in some of them is not out of sync. Definitely need to work out how to make the tests more robust/introduce an acceptable margin of error before automating data updates.

[fershad]

Update grid intensity data for 2022 in CO2.js

[mrchrisadams]

Hey fish, i'm happy to merge this in.