Bump go.opentelemetry.io/otel/sdk from 1.28.0 to 1.29.0 in /otlp #264

Job	Run time
Test (stable)	35s
Test (oldstable)	8s
Test (otlp, stable)	50s
Test (otlp, oldstable)	25s
Test (gcp, stable)	53s
Test (gcp, oldstable)	39s
Test (grpc, stable)	53s
Test (grpc, oldstable)	27s
Test (examples/grpc, stable)	1m 7s
Test (examples/grpc, oldstable)	39s
Test (http, stable)	52s
Test (http, oldstable)	27s
Test (examples/http, stable)	1m 2s
Test (examples/http, oldstable)	33s
All Tests	1s
	9m 31s

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