libwebrtc を m130.6723.2.0 にアップデート

[torikizi]

libwebrtc を m130.6723.2.0 にアップデートしました。

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This pull request includes updates to various dependencies and code refactoring to replace absl::optional with std::optional. The most important changes include updating the WebRTC version, modifying header files to include <optional>, and refactoring the code to use std::optional instead of absl::optional.

Dependency updates:

• Updated WebRTC version from m129.6668.1.1 to m130.6723.2.0 in CHANGES.md, VERSION, and examples/VERSION files. [1] [2] [3]

Code refactoring:

• Added #include <optional> to nvcodec_video_decoder.h and vpl_video_decoder.h header files. [1] [2]
• Changed absl::optional to std::optional in scalable_track_source.h and scalable_track_source.cpp. [1] [2]
• Replaced absl::nullopt with std::nullopt in nvcodec_video_decoder.cpp and vpl_video_decoder.cpp. [1] [2]

[miosakuma]

対応ありがとうございます！

[torikizi]

確認ありがとうございました。こちらマージします。