Add exclude google.golang.org/grpc/stats/opentelemetry v0.0.0-20240907200651-3ffb98b2c93a to go.mod
according to https://github.com/googleapis/google-cloud-go/issues/11283#issuecomment-2558515586 .
This fixes the following strange issue on `make vendor-update`:
cloud.google.com/go/storage imports
google.golang.org/grpc/stats/opentelemetry: ambiguous import: found package google.golang.org/grpc/stats/opentelemetry in multiple modules:
google.golang.org/grpc v1.69.0 (/go/pkg/mod/google.golang.org/grpc@v1.69.0/stats/opentelemetry)
google.golang.org/grpc/stats/opentelemetry v0.0.0-20240907200651-3ffb98b2c93a (/go/pkg/mod/google.golang.org/grpc/stats/opentelemetry@v0.0.0-20240907200651-3ffb98b2c93a)