Don't override Halibut TLS configuration

[rhysparry]

Background

In Always use system TLS defaults (Halibut#706) Halibut is removing the ability to configure TLS protocols, instead delegating to the underlying Operating System.

This PR updates Tentacle to allow Halibut to use Operating System TLS configruation.

Results

• Removal of the OCTOPUS_TENTACLE_USE_LEGACY_TLS override, which would allow explicitly setting all TLS protocols as supported.
• Halibut's default configuration, deferring to the Operating System, will define the available TLS versions
• Resolves EFT-156

Before

• Users could fallback to old Tentacle behaviour that enabled all available TLS protocols using the OCTOPUS_TENTACLE_USE_LEGACY_TLS environment variable.

After

• The OCTOPUS_TENTACLE_USE_LEGACY_TLS will have no effect. The Operating System default enabled TLS protocols will be used. The new behaviour will be as if the environment variable was not set.

If you Operating System is misconfigured you may not have access to newer TLS protocols required to connect to Octopus Server.

How to review this PR

Quality ✔️

Pre-requisites

• I have read How we use GitHub Issues for help deciding when and where it's appropriate to make an issue.
• I have considered informing or consulting the right people, according to the ownership map.
• I have considered appropriate testing for my change.