Supported readers page does not include many readers

[adybbroe]

Describe the bug
The table with the supported readers at the RTD pages does not seem to update correctly.
I was looking for the EPSSG MWI/ICI which was added by a recent PR, but can't find them?

To Reproduce

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Expected behavior
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Actual results
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Environment Info:

• OS: [e.g. OSX, Windows, Linux]
• Satpy Version: [e.g. 0.9.0]
• PyResample Version:
• Readers and writers dependencies (when relevant): [run from satpy.utils import check_satpy; check_satpy()]

Additional context
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[djhoese]

The problem isn't that it isn't updating, it is that it is completely not including readers that are missing dependencies on the readthedocs environment.

CC @BENR0