Linux x86_64 版のビルドプラットフォームを ubuntu-22.04_x86_64 にあげる

[miosakuma]

• Linux のビルドプラットフォームを ubuntu-22.04_x86_64 にあげる
  • Sora C++ SDK も ubuntu-22.04_x86_64 となる
• Linux と Android のビルド環境を ubuntu-22.04_x86_64 にあげる

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This pull request includes several changes to update the GitHub Actions workflow and documentation to use Ubuntu 22.04 instead of Ubuntu 20.04. The most important changes involve modifying the workflow configuration and updating the CHANGES.md file to reflect these updates.

Updates to GitHub Actions workflow:

• .github/workflows/build.yml: Changed the matrix name from ubuntu-20.04_x86_64 to ubuntu-22.04_x86_64 and updated the runs-on field accordingly.
• .github/workflows/build.yml: Updated the if conditions to check for ubuntu-22.04_x86_64 instead of ubuntu-20.04_x86_64. [1] [2]
• .github/workflows/build.yml: Modified the paths and artifact names to use ubuntu-22.04_x86_64 instead of ubuntu-20.04_x86_64. [1] [2]

Documentation updates:

• CHANGES.md: Added entries to document the changes in the build environment from Ubuntu 20.04 to Ubuntu 22.04.