Bump github.com/DataDog/datadog-agent/pkg/proto from 0.63.0-devel to 0.64.0-devel in /pkg/otlp/metrics

Bump github.com/DataDog/datadog-agent/pkg/proto from 0.63.0-devel to 0.64.0-devel in /pkg/otlp/metrics #1867