Remove -Resume parameter from Invoke-Webrequest commands in task setup

[rmunn]

In #850 I used the Powershell command Invoke-WebRequest -Resume, which was introduced in Powershell 6.1. I did not realize that even on Windows 11, the Powershell version that ships with the OS is Powershell 5.1, and to get the latest version of Powershell 6 or higher (currently 7.4) you need to download an .msi file from GitHub. (Also, the command name changed from powershell to pwsh).

We need to either:

• remove the -Resume part of the Invoke-WebRequest command (and skip running it if the .zip file matches a checksum, making the setup-win script more complicated but able to run on powershell 5.1), or
• add a step to download and install a modern version of Powershell before running the Invoke-WebRequest command, so that we can then count on modern pwsh features and bugfixes to be present.

[rmunn]

Looks like -Resume is buggy anyway: although PowerShell/PowerShell#13982 is marked as completed, it's still happening. If you pass -Resume when the file already exists, PowerShell throws a NullReferenceError. I suspect that this line is to blame, but I'm not going to spend time troubleshooting PowerShell; that's a total waste of my time. We'll just check that the zip file matches a checksum (which we will check into Git so that we can change it later if we upload a different version of the sena-3.zip file, for example), and skip the download if the checksum matches. If it doesn't match, we'll download without -Resume, which is documented to overwrite any existing files.

[hahn-kev]

let's just remove the -Resume

[rmunn]

The valid SHA256 checksums for sena-3.zip and elawa.zip, which you should hardcode into the Taskfile.yml, are:

• sena-3.zip: bec5131799db07bf8d84d8fc1f3169fb2574f2a1f4c37f6898eab563a4ae95b8
• elawa.zip: e3608f1e3188ce5fdb166fbf9d5aad06558db68efa079fb453881572b50cb8e3