ci: fix CodeQL C/C++ build by switching to ubuntu-24.04

[Copilot]

The CodeQL "Analyze (c-cpp)" job was failing due to an incompatibility between nlohmann-json 3.10.x (shipped by ubuntu-22.04) and gcc-14 from the toolchain PPA — specifically, the newer libstdc++ made implicit conversion from nlohmann::basic_json<>::value_type to std::vector<std::string> ambiguous at assignment sites like:

Mimetypes = jsonData["server"]["mimetypes"];  // ambiguous operator= with nlohmann 3.10.x + gcc-14

Changes

• .github/workflows/codeql.yml
  • Switch runner from ubuntu-22.04 → ubuntu-24.04, which ships gcc-14/g++-14 natively and nlohmann-json 3.11.x (resolves the ambiguous conversion)
  • Remove software-properties-common, add-apt-repository, and the ubuntu-toolchain-r/test PPA steps — no longer needed

[Copilot]

Pull request overview

This pull request updates the CodeQL workflow runner to Ubuntu 24.04 to resolve a C/C++ CodeQL build failure caused by the Ubuntu 22.04 + gcc-14 toolchain PPA combination (notably around nlohmann-json 3.10.x with newer libstdc++).

Changes:

• Switch CodeQL “Analyze (c-cpp)” job runner from ubuntu-22.04 to ubuntu-24.04.
• Remove the toolchain PPA bootstrap steps (software-properties-common, add-apt-repository, ppa:ubuntu-toolchain-r/test) since they’re no longer needed on 24.04.

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