'channel' parameter is superfluous if also using a 'version' parameter.

Author: John Beisner

run-build.ps1

@@ -68,8 +68,8 @@ $env:VSTEST_TRACE_BUILD=1
 # install a stage0
 $dotnetInstallPath = Join-Path $RepoRoot "scripts\obtain\dotnet-install.ps1"
 
-Write-Output "$dotnetInstallPath -Channel ""master"" -version ""2.1.0-preview1-007172"" -InstallDir $env:DOTNET_INSTALL_DIR -Architecture ""$Architecture"""
-Invoke-Expression "$dotnetInstallPath -Channel ""master"" -version ""2.1.0-preview1-007172"" -InstallDir $env:DOTNET_INSTALL_DIR -Architecture ""$Architecture"""
+Write-Output "$dotnetInstallPath -version ""2.1.0-preview1-007172"" -InstallDir $env:DOTNET_INSTALL_DIR -Architecture ""$Architecture"""
+Invoke-Expression "$dotnetInstallPath -version ""2.1.0-preview1-007172"" -InstallDir $env:DOTNET_INSTALL_DIR -Architecture ""$Architecture"""
 if ($LastExitCode -ne 0)
 {
     Write-Output "The .NET CLI installation failed with exit code $LastExitCode"