match_cases() example not working with lab data about lab2godata

[AmyMikhail]

Update:

The godataR::get_labresults_epiwindow() function is working fine, but there is currently a problem with the WHO servers that house R13 and R21 instances of Go.Data not accepting the dollar sign in POST requests where the JSON query is in the body of the request and the $in condition has been used. This may not be a problem on other servers, but the solution applied here will also be informative if other users encounter this issue on their own servers. Solving it will also help to ensure that the WHO servers can be used to demonstrate the full functionality of the lab2godata app.