Replace PPC g++-10 with g++14.

It looks like g++-10 has a bunch of compiler issues.

Through some debugging/print statements, it looks like sometimes a static_cast<float>(double) produces 0 for inputs like 0.224. Adding print statements fixes the issue, adding other explicit casts fixes the issue, re-arranging statements fixes the issue. There are no such issues with clang, or with newer versions of g++-powerpc64le-linux-gnu.

Our CI had a bunch of failures ever since removing the PPC runner.