[mgt] Hide allow http response header

[MarcialRosales]

Proposed Changes

Hide allow http response header except for 405 responses. This behaviour is configurable. By default, RabbitMQ keeps sending this header.
This is a requested security improvement.

Accompanied by docs PR: rabbitmq/rabbitmq-website#2562

Types of Changes

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• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI

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