Move doxygen generation to nightly only (#82573)
as it is OOMing yet again (8 out of 28 commits on friday)
a milder version of https://github.com/pytorch/pytorch/pull/80451
Pull Request resolved: https://github.com/pytorch/pytorch/pull/82573
Approved by: https://github.com/jbschlosser, https://github.com/ZainRizvi, https://github.com/malfet
