Simplify example blob_05_default_credential.rs (#1373) #3736

Job	Run time
Code Style	5m 1s
Get minimum supported rust version	14s
test AutoRust	3m 26s
SDK Tests (stable, false)	8m 40s
SDK Tests (1.70.0, false)	10m 1s
SDK Tests (nightly, true)	8m 8s
Integration Tests (stable, false)	8m 13s
Integration Tests (1.70.0, false)	8m 5s
Integration Tests (nightly, true)	8m 57s
E2E Tests (stable, false)	57s
E2E Tests (1.70.0, false)	58s
E2E Tests (nightly, true)	1m 0s
Services Tests (stable, false)	25m 23s
Services Tests (1.70.0, false)	24m 52s
Services Tests (nightly, true)	43m 35s
	2h 37m 30s

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