Remove add command

[anamnavi]

PR Summary

For internal compliance reasons we will not be downloading the powershell package from online (through ADD or curl) directly into our images.

PR Checklist

• [x] PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• [x] Summarized changes
• [x] Change is not breaking
• [x] Make sure all Dockerfile, .sh, .ps1 and .psm1 files have the correct copyright header
• [x] This PR is ready to merge and is not Work in Progress.
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[anamnavi]

I'll look at the WebClient DownloadFile() error later today

[RDIL]

What exactly is the reasoning behind this change?

[anamnavi]

@RDIL for internal compliance reasons we don't want to be downloading powershell package from online (through ADD or curl) directly into our images

[RDIL]

What is the plan for getting the package into the images then?

[anamnavi]

@RDIL users will run the build script first, which will download the powershell installer file, then in the image we copy that installer file in and install the package.