[release/10.0.2xx] pwsh missing for some containers

[mthalman]

The changes in dotnet/dotnet#3219 introduced a dependency on PowerShell being installed in the container where the build jobs run.

This is missing for the following container images:

• mcr.microsoft.com/dotnet-buildtools/prereqs:almalinux-8-source-build
• mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-24.04

This causes the following error in the Generate delegation SAS Token for dotnetbuilds/internal build step:

##[error]Script failed with error: Error: Unable to locate executable file: 'pwsh'. Please verify either the file path exists or the file can be found within a directory specified by the PATH environment variable. Also check the file mode to verify the file is executable.

[mmitche]

dotnet/dotnet-buildtools-prereqs-docker#1541 and dotnet/dotnet-buildtools-prereqs-docker#1541