Fixes incorrect error message on passed ScriptBlock by -Variables

[santisq]

Fixes incorrect method call on AddVariables extension method.

Invoke-Parallel v1.1.6

PS \> $null | Invoke-Parallel { $var } -Variables @{ var = {} }
# Invoke-Parallel: A $using: variable cannot be a script block. Passed-in script block variables are not supported, and can result in undefined behavior.

Invoke-Parallel v1.1.7

PS \> $null | Invoke-Parallel { $var } -Variables @{ var = {} }
# Invoke-Parallel: Passed-in script block variables are not supported, and can result in undefined behavior.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.85%. Comparing base (d947183) to head (e1f1957).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #34      +/-   ##
==========================================
+ Coverage   88.99%   90.85%   +1.86%     
==========================================
  Files           9        9              
  Lines         536      536              
  Branches       40       40              
==========================================
+ Hits          477      487      +10     
+ Misses         49       39      -10     
  Partials       10       10              

Flag	Coverage Δ
PS-5.1	90.54% <ø> (+2.25%)	⬆️
PS-7_Linux	90.85% <100.00%> (+1.86%)	⬆️
PS-7_Windows	90.54% <ø> (+2.25%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.