Set web_hooks_disable_failed to default false

What does this MR do and why?

This change toggles an ops feature flag called auto_disabling_web_hooks to be default_enabled: false.

An explanation of this change can be read here !114508 (comment 1312315884).

This will allow the existing feature to become opt-in, default disabled, for self-managed instances #390157 (closed).

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #390157 (closed)