docs(storage): replace deprecated usage of ioutil in sample code

[sfc-gh-kleonhard]

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[tritone]

Thanks for your contribution!

There are a bunch of other uses of ioutil elsewhere in this package, but we can clean them up separately.

To merge this PR, we'll need you to sign the CLA; there is a link below.

[sfc-gh-kleonhard]

Thanks for your contribution!

There are a bunch of other uses of ioutil elsewhere in this package, but we can clean them up separately.

To merge this PR, we'll need you to sign the CLA; there is a link below.

Thanks Chris, got the CLA taken care of.