PS: Fix parameter/argument name mapping for named parameters

[MathiasVP]

Another missing flow found by Chanel!

Because PowerShell is case insensitive you can do stuff like:

function Foo {
  param($myParAm)

  Write-Output $myParAm
}

Foo -MyPARAM "Hello"

In dataflow we need to "normalize" all the parameter names by lower-casing them. And apparently I had forgotten to lower-case the parameter names 🤦