Update github action to create a mac os "universal" build.

[bpow]

Just in case people want to curate on an older intel-based mac.

[pnrobinson]

@bpow
please check if the "old" mac installer works on your side:
https://github.com/P2GX/phenoboard/releases/tag/v0.5.124
If so, we still need to add some documentation to the install page about which one to download.

[pnrobinson]

@bpow I am sorry I had to revert to the previous build, because the combined build seemed to destroy the styling for newer macs. I am not able to debug myself on an old mac because we just have M1-4s. If this is important, we could find a time to zoom to get both ends to work. Please reopen as needed.