Bump go.opentelemetry.io/otel/sdk from 1.30.0 to 1.31.0 in /otlp #303

Job	Run time
Test (stable)	30s
Test (oldstable)	34s
Test (otlp, stable)	55s
Test (otlp, oldstable)	49s
Test (gcp, stable)	49s
Test (gcp, oldstable)	54s
Test (grpc, stable)	51s
Test (grpc, oldstable)	1m 0s
Test (examples/grpc, stable)	1m 6s
Test (examples/grpc, oldstable)	1m 2s
Test (http, stable)	50s
Test (http, oldstable)	47s
Test (examples/http, stable)	59s
Test (examples/http, oldstable)	59s
All Tests	1s
	12m 6s

Provide feedback