Update custom_authentication_provider.rst

Removed response because it will always be overwritten "By default deny authorization" response
minor #3929 Update custom_authentication_provider.rst (verschoof)

This PR was submitted for the 2.5 branch but it was merged into the 2.4 branch instead (closes #3929).

Discussion
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Update custom_authentication_provider.rst

Removed response because it will always be overwritten "By default deny authorization" response

Commits
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d136ac8 Update custom_authentication_provider.rst