Bump cloud.google.com/go/compute/metadata from 0.4.0 to 0.5.0 in /gcp #243

Job	Run time
Test (http, stable)	45s
Test (stable)	40s
Test (oldstable)	38s
Test (examples/http, stable)	55s
Test (otlp, stable)	48s
Test (otlp, oldstable)	49s
Test (gcp, stable)	57s
Test (gcp, oldstable)	58s
Test (grpc, stable)	57s
Test (grpc, oldstable)	59s
Test (examples/grpc, stable)	57s
Test (examples/grpc, oldstable)	1m 2s
All Tests	1s
	10m 26s

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