A couple of fixes to lab exercise in Chapter 3

[youngroklee-ml]

I assign the copyright of this contribution to Alex Gold.

In Step 3 of Lab exercise in Chapter 3: "Build a Shiny App"

• In Python app, key in dictionary should be "sex_male" with lowercase "m"
• In R app, argument of http2::req_body_json() should be a list of a list, so pass list(vals()) as an argument

[akgold]

Thanks @youngroklee-ml!