docs(changelog): record Chapel 2.8.0 ubuntu-22.04 runs-on pin (#183) (#224)

Chapel 2.8.0's debian package is linked against libclang-cpp.so.14
(LLVM-14 / Ubuntu 22.04). On ubuntu-latest (24.04) apt resolves the
unmet dependency with libclang-cpp-18, leaving chpl unable to load. PR
#183 pinned the runner to ubuntu-22.04 and switched to apt-get install
-y /tmp/chapel.deb for declarative resolution.

Author: hyperpolymath