Remove separate calculated illuminance data point for lux

[bachya]

Describe what the PR does:

We previously always calculated solarradiation_lux if solarradiation was present. However, now that we have unit conversion, lux is merely an output unit option and shouldn't be a separate sensor.

Does this fix a specific issue?

N/A

Checklist:

• Confirm that one or more new tests are written for the new functionality.
• Run tests and ensure everything passes (with 100% test coverage).
• Update README.md with any new documentation.
• Add yourself to AUTHORS.md.

[codecov]

Codecov Report

Merging #341 (8a1739e) into dev (9366a40) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##               dev      #341   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           29        29           
  Lines         1486      1482    -4     
=========================================
- Hits          1486      1482    -4     

Impacted Files	Coverage Δ
ecowitt2mqtt/const.py	100.00% <ø> (ø)
ecowitt2mqtt/data.py	100.00% <ø> (ø)
ecowitt2mqtt/helpers/publisher/hass.py	100.00% <ø> (ø)
ecowitt2mqtt/helpers/calculator/illuminance.py	100.00% <100.00%> (ø)

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