Clear up Install-ChocolateyPackage examples

From @chrisdent on PowerShell discord server:

>Install-ChocolateyPackage, the examples are a bit all over the place. There's variables which aren't declared in example 3 for instance. The -File parameter needs better documentation too. It's unclear if this can be used to replace Install-ChocolateyInstallPackage (my colleague was trying to use it). I can raise an issue if you like, but you guys have a fair selection of those

Locate the Install-ChocolateyPackage documentation and review each example, starting with example 3 and the -File parameter description. Compare the documented purpose with Install-ChocolateyInstallPackage. Done means all example variables are defined and the parameter behavior and relationship between the two commands are clear.

Written by the indexing model from the issue text.