Update air quality data

[alexander-griffen]

Fixes #180

Update air quality data to use more recent data and also include WHO standards

This currently does not show up in the UI. Additionally, the following tasks need to be completed on this work:

• Finding a way to show the WHO standards in the UI
• Possibly finding more WHO standards, as I only could find them for some of the pollutants

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.44%. Comparing base (461d65c) to head (888c3bf).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #520      +/-   ##
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- Coverage   82.59%   82.44%   -0.15%     
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  Files         104      104              
  Lines        3435     3487      +52     
  Branches      345      366      +21     
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+ Hits         2837     2875      +38     
- Misses        512      524      +12     
- Partials       86       88       +2     

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[zarino]

We have a choice here – do we want to just get out a quick change that updates from 2021 to 2022 Defra pollutant data, or do we want to incorporate WHO guidelines?

If this PR is just about updating from 2021 to 2022 Defra data, then:

• We should remove the WHO_AQG stuff.
• We should fix the display of this data on the constituency page – the figures should be rounded floats, not percentages, and should probably just be a table, rather than a bar chart, because comparing bars for totally different pollutants on different scales makes no sense.

If this PR is also about making the air quality data easier to understand, by comparing with WHO guidelines, I’m thinking we should:

• EITHER create a separate dataset that presents comparative figures (ratio? percentage?) for just the three pollutants we have comparable data for.
• OR keep it all in one dataset, but create a custom set of comparators for this dataset, so that users can select options like "is above WHO guidelines" and "is below WHO guidelines", in addition to the normal "is equal to or greater than" / "is less than" options. (This feels like more work to me, and still not as flexible as the separate dataset option.)

I’ve added more detail on this to the original ticket at #180