jsonhelp-964283: Update toJson to not serialize defaultValue
jsonhelp-964283: Update toJson to not serialize defaultValue

We really need to support defaultText as a replacement, but that’s
going to take more work so for now we just use a dummy value.

Signed-off-by: Joe Walker <7a17872fbb32c7d760c9a16ee3076daead11efcf@mozilla.com>

joewalker/gcli,mozilla/gcli,mozilla/gcli,joewalker/gcli,mozilla/gcli