Ax 1.2.1

Bug fixes

• Improved error messaging for client.compute_analyses when certain analyses are
  not yet available (#4441)
• Fix tooltip mismatch bug in ArmEffectsPlot (#4479)

Other changes

• Bumped pinned botorch version to 0.16.1 (#4570)
• Removed deprecated robust optimization functionality (#4493)
• Allow HierarchicalSearchSpace to be constructed with multiple root nodes (#4560)