Update Invoke-Pester help

[Frode Flaten]

Checklist

• Issue has a meaningful title
• I have searched the existing issues. See open documentation issues

Where did you see it?

Pester (latest)

Function name

Invoke-Pester

What is the issue?

The help for Invoke-Pesterstill includes docs for legacy-parameters and syntax that's not implemented.

E.g.

• Strict and PesterOption has help when they're ignored.
  Should Strict be reimplemented? Mentioned as possibility for 5.1.0 in 5.0.1 relase notes
• Mentions to Strict, Show, hashtable ++ in description and other options
  Also reference to Strict in It help.
• Remove "(introduced v5)"
• Is Simple parameter set really deprecated, ex. -ExcludePath? If so, avoid all mentions in description?

[Frode Flaten]

Should decide on #2493 first