[docs] Use env var for state store examples

[elithrar]

This makes it easier for users to copy/paste examples earlier in the guide, and adds a (touch) of clarity about bucket names.

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[elithrar]

Updated commit with corp email address so that it associates with the CLA.

[justinsb]

/check-cla

[rdrgmnzs]

/lgtm

[chrisz100]

/ok-to-test
/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chrisz100, elithrar

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