Update Azure SDK logger variable in docs

[ram-parameswaran]

Update Azure secrets engine docs to use AZURE_SDK_GO_LOGGING for Azure debug

Description

What does this PR do?

TODO only if you're a HashiCorp employee

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  • If this fixes a critical security vulnerability or severity 1 bug, it will also need to be backported to the current LTS versions of Vault. To ensure this, use all available enterprise labels.
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  of a public function, even if that change is in a CE file, double check that
  applying the patch for this PR to the ENT repo and running tests doesn't
  break any tests. Sometimes ENT only tests rely on public functions in CE
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