Removed mention of and workaround for 32-bit x86
The support for it is deprecated since version 2020 and removed since version 2022.
The workaround for GCC -O3 optimization bug anyhow seems unnecessary as tests pass or fail exactly the same without it when using GCC 11+, which is the minimum version we now target.
Refs #3205 (closed)
Edited by Vedran Miletić