NHSN doc changes

[aysim319]

addresses issue(s) #2125

Summary:

doc changes for NHSN

8 new NHSN signals were added by 2 PRs:

• 2085 add proportions nhsn covidcast-indicators#2111
• first implimentation of rsv covidcast-indicators#2121

(both PRs were released to production as part of cmu-delphi/covidcast-indicators#2126 )

They consist of the 4 listed at https://github.com/cmu-delphi/covidcast-indicators/blob/454ac565d0a0f2b5cf557e4efb2278c278c528a9/nhsn/delphi_nhsn/constants.py#L18-L21 as well as the associated "_prelim" versions of each.

Prerequisites:

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

[nmdefries]

Please check the wording changes I made. After those are included, this is good to go.

[aysim319]

@carlynvandyke thanks for catching my numerous copy pastas 😅 hopefully i fixed it this time around

[melange396]

you could fix some of the spacing to make the table line up better in the raw file, but it doesnt affect the rendered version. otherwise, it looks good to me!

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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