Adding the linux feed removal to 6.0.1xx as I figured out the issue (#30037)

Author: marcpopMSFT

build/RunTestsOnHelix.sh

@@ -11,3 +11,14 @@ cp -a $HELIX_CORRELATION_PAYLOAD/t/TestExecutionDirectoryFiles/. $TestExecutionD
 
 # call dotnet new so the first run message doesn't interfere with the first test
 dotnet new --debug:ephemeral-hive
+
+dotnet nuget list source --configfile $TestExecutionDirectory/NuGet.config
+dotnet nuget remove source dotnet6-transport --configfile $TestExecutionDirectory/NuGet.config
+dotnet nuget remove source dotnet6-internal-transport --configfile $TestExecutionDirectory/NuGet.config
+dotnet nuget remove source richnav --configfile $TestExecutionDirectory/NuGet.config
+dotnet nuget remove source vs-impl --configfile $TestExecutionDirectory/NuGet.config
+dotnet nuget remove source dotnet-libraries-transport --configfile $TestExecutionDirectory/NuGet.config
+dotnet nuget remove source dotnet-tools-transport --configfile $TestExecutionDirectory/NuGet.config
+dotnet nuget remove source dotnet-libraries --configfile $TestExecutionDirectory/NuGet.config
+dotnet nuget remove source dotnet-eng --configfile $TestExecutionDirectory/NuGet.config
+dotnet nuget list source --configfile $TestExecutionDirectory/NuGet.config