correct NewProtocol6ProviderServerWithError to match the sdkv2 defini…

.changelog/303.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+tfsdk: Correct `NewProtocol6ProviderServerWithError` function signature to align to sdk v2 `TestCase.ProtoV6ProviderFactories`
+```

tfsdk/serve.go

@@ -50,12 +50,12 @@ func NewProtocol6ProviderServer(p Provider) func() tfprotov6.ProviderServer {
 // acceptance testing helper/resource.TestCase.ProtoV6ProviderFactories.
 //
 // The error return is not currently used, but it may be in the future.
-func NewProtocol6ProviderServerWithError(p Provider) (func() tfprotov6.ProviderServer, error) {
-	return func() tfprotov6.ProviderServer {
+func NewProtocol6ProviderServerWithError(p Provider) func() (tfprotov6.ProviderServer, error) {
+	return func() (tfprotov6.ProviderServer, error) {
 		return &server{
 			p: p,
-		}
-	}, nil
+		}, nil
+	}
 }
 
 // Serve serves a provider, blocking until the context is canceled.

tfsdk/serve_test.go

@@ -33,14 +33,12 @@ func TestNewProtocol6ProviderServer(t *testing.T) {
 func TestNewProtocol6ProviderServerWithError(t *testing.T) {
 	provider := &testServeProvider{}
 
-	providerServerFunc, err := NewProtocol6ProviderServerWithError(provider)
+	providerServer, err := NewProtocol6ProviderServerWithError(provider)()
 
 	if err != nil {
 		t.Fatalf("unexpected error creating ProviderServer: %s", err)
 	}
 
-	providerServer := providerServerFunc()
-
 	// Simple verification
 	_, err = providerServer.GetProviderSchema(context.Background(), &tfprotov6.GetProviderSchemaRequest{})