[doc] Remove obsolete doc configuration
[doc] Remove obsolete doc configuration

Closes https://github.com/google/iree/pull/1902

COPYBARA_INTEGRATE_REVIEW=https://github.com/google/iree/pull/1902 from antiagainst:rm-unused-config 66d068993da4a44885d34b824e06a22c786887d1
PiperOrigin-RevId: 311331924

google/iree,google/iree,iree-org/iree,iree-org/iree,google/iree,google/iree,iree-org/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,google/iree,iree-org/iree,iree-org/iree