obs-outputs: Enable HDR for HEVC over RTMP

[nquah]

Removes flag guard to enable HDR streaming for HEVC over enhanced-RTMP. This functionality is currently only supported by YouTube. See github.com/veovera/enhanced-rtmp for the enhanced-RTMP spec.

Description

HDR support for RTMP was previously added in #8522, according to the enhanced-RTMP spec at github.com/veovera/enhanced-rtmp. This change partially removes the flag guard, to enable streaming HDR with HEVC over RTMP.

Motivation and Context

Enables streaming HDR with HEVC over RTMP to YouTube.

Notes:

• Streaming HDR with HEVC to YouTube is already supported via HLS in OBS. This enables the capability via RTMP.
• Streaming HDR with AV1 over RTMP to YouTube is not officially supported at this time.

How Has This Been Tested?

Tested against YouTube with Nvidia RTX 4090, Intel Arc A750, AMD RX 7900 XTX.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[Fenrirthviti]

As a note, this requires #10028 to be resolved first.

[RytoEX]

Looks fine. I don't think we need to block on #10028. The main known benefit of #10028 is to mitigate a bug with AMD users on outdated drivers. AMD users on current drivers should have no issues.