Remove AVX2 requirement on Linux

[blacklightpy]

The Linux build requires AVX2. The browser runs perfectly well on Windows without it. But I can't run it on Linux on the same machine.

[nightchieftain]

I second this. Just got the Illegal instruction (core dumped) pulse-browser thing.
Read in the older reopened issue that lack of avx2 support on behalf of my CPU is probably the reason.
Please do consider removing the aforementioned requirement. Firefox-integrated browser with a smaller footprint would be a godsend on my older Arch machine.

[splatboydev]

I would merge the fix on gluon if I had the permissions, but I doubt it'll ever be fixed after seeing the readme.