Remove the vendored testprovider_go

Its only consumer was TestDotnetErrorHooks, which was removed in favor
of the l2-resource-hook-on-error conformance test.

Author: iwahbe

integration_tests/go.mod

@@ -11,7 +11,6 @@ require (
 	github.com/pulumi/pulumi/sdk/v3 v3.253.1-0.20260717102922-cd588358a197
 	github.com/stretchr/testify v1.11.1
 	google.golang.org/grpc v1.82.0
-	google.golang.org/protobuf v1.36.11
 )
 
 require (
@@ -217,6 +216,7 @@ require (
 	google.golang.org/genproto v0.0.0-20260316180232-0b37fe3546d5 // indirect
 	google.golang.org/genproto/googleapis/api v0.0.0-20260713224248-f5fc221cf8c4 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260713224248-f5fc221cf8c4 // indirect
+	google.golang.org/protobuf v1.36.11 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	lukechampine.com/frand v1.5.1 // indirect
 )