Use Aspnetcore 6.0 in universal builder acceptance test

PiperOrigin-RevId: 796384439
Change-Id: Ic75bb2c1e68b2674ff72a31a7bec4e9d12b1e3bb

Author: srinjoyray

builders/gcp/base/acceptance/dotnet_fn_test.go

@@ -30,9 +30,10 @@ func TestAcceptanceDotNetFn(t *testing.T) {
 	testCases := []acceptance.Test{
 		// When there is only one target, we don't need to set FUNCTION_TARGET.
 		{
+			// .NET 3.1 is not supported on Ubuntu 22.04.
 			Name:       "cs single target",
 			App:        "cs_single_target",
-			SkipStacks: []string{"google.24.full", "google.24"},
+			SkipStacks: []string{"google.24.full", "google.24", "google.22", "google.gae.22"},
 			Path:       "/function",
 			MustUse:    []string{dotnetRuntime, dotnetPublish},
 			MustNotUse: []string{entrypoint},

builders/testdata/dotnet/functions/cs_multiple_targets/TestFunction.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>netcoreapp6.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>

builders/testdata/dotnet/generic/simple/simple.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>netcoreapp6.0</TargetFramework>
   </PropertyGroup>
 
 </Project>