Ubuntu 20.04 LTS (CI) runner will be removed

[lum1n0us]

This is a scheduled Ubuntu 20.04 brownout. Ubuntu 20.04 LTS runner will be removed on 2025-04-15. For more details, see actions/runner-images#11101

[lum1n0us]

ubuntu-20.04 are used in https://github.com/search?q=repo%3Abytecodealliance%2Fwasm-micro-runtime+ubuntu-20.04+path%3A%2F%5E%5C.github%5C%2Fworkflows%5C%2F%2F&type=code

• .github/workflows/release_process.yml
• .github/workflows/coding_guidelines.yml
• .github/workflows/build_llvm_libraries.yml
• .github/workflows/nightly_run.yml
• .github/workflows/compilation_on_sgx.yml

---

https://download.01.org/intel-sgx/latest/linux-latest/distro/

[yamt]

we no longer use ubuntu-20.04 after #4191. let's close.