docs: fix typo in FakeGoogleCloudStorage example

[alexandear]

This PR corrects a typo.

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
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  I confirm that I got approval (please contact security@ory.sh) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
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[codecov]

Codecov Report

Merging #434 (d33396c) into v3 (e733223) will not change coverage.
The diff coverage is n/a.

❗ Current head d33396c differs from pull request most recent head 96dba47. Consider uploading reports for the commit 96dba47 to get more accurate results

@@           Coverage Diff           @@
##               v3     #434   +/-   ##
=======================================
  Coverage   53.95%   53.95%           
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  Files           1        1           
  Lines         341      341           
=======================================
  Hits          184      184           
  Misses        121      121           
  Partials       36       36           

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