Problem with PowerShell ExecutionPolicy

[lovettchris]

See https://leanprover.zulipchat.com/#narrow/stream/270676-lean4/topic/VSCode.20.22Waiting.20for.20lean.20server.20to.20start.2E.2E.2E.22

Students may not know how to run Set-ExecutionPolicy -ExecutionPolicy Unrestricted -Scope CurrentUser needed in order for elan-init.ps1 to work.

We could run it for them before running elan-init.ps1 then set it back to whatever level it was before. We can also set a safer level of Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser which still works because elan-init.ps1 is run locally, not remotely.