refnx/refnx: REL: v0.1.24

0.1.24 use oldest-supported-numpy to ensure that older numpy versions are used to build refnx wheels. This will allow refnx to be used with more recent versions as well as the oldest version supported on a given Python version. Previously refnx wheels were built with the newest numpy available at build time, and were probably not compatible with older numpy versions. Rejig the build process to make macOS universal wheels