docs: clarify subject-case

[olets]

Expected Behavior

1. The reference-rules standard is for the condition to say that found value "is in case value".
2. The comments in the possible values follow a standard pattern

Current Behavior

1. subject-case docs specifies the default value's value in the condition.
2. subject-case's "possible values" includes

   'lower-case',    // default
   

   which is an outlier compared to the rest of that code block, which uses the form

   'upper-case',    // UPPERCASE
   

Affected packages

• cli
• core
• prompt
• config-angular

Possible Solution

1. Change subject-case's condition language
2. Change subject-case's "possible values" to use // lower case instead of // default

Context

I was modifying my subject-case config, and needed to see what the possible options were.