Add google-symptoms conjunctivitis to signals spreadsheet and API documentation

[carlynvandyke]

Two new signals went in with PR cmu-delphi/covidcast-indicators#2112 : google-symptoms:s07_raw_search and google-symptoms:s07_smoothed_search

[aysim319]

@nmdefries for visibility

[melange396]

spreadsheet/CSV changes should be going in with #1612

still need to update the docs at https://github.com/cmu-delphi/delphi-epidata/blob/dev/docs/api/covidcast-signals/google-symptoms.md?plain=1