Assorted dashboard cleanup tasks

[rzats]

Closes #1233.

Prerequisites:

• [X] Unless it is a hotfix it should be merged against the dev branch
• [X] Branch is up-to-date with the branch to be merged with, i.e. dev
• [x] Build is successful
• [X] Code is cleaned up and formatted

Summary

Implements the changes requested for the Covidcast dashboard:

• Removes the top section (7-day averages and comparisons).
• Moves the COVID hospital admissions chart to top of page (above the beehive map).
• Removes COVID cases from the indicators table.
• Replaces JHU deaths (jhu-csse deaths_7dav_incidence_prop) with NCHS deaths (nchs-mortality deaths_covid_incidence_prop).

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[melange396]

once we are settled on the new signals, we should remember to update them here as well: https://github.com/cmu-delphi/delphi-epidata/blob/ea84e372ce0b0f3549c62b74fa439374b19f15f6/docs/api/covidcast_signals.md?plain=1#L33-L41

[melange396]

Superseded by #1235 which updated signal names and (temporarily) removed the top "overview" table widget.