[llvm] Delete assignment operator from `MachineBlockFrequencyInfo` (PR #101289)

[via llvm-commits]

abhishek-kaushik22 wrote:

Sorry 😢 , this looks like a mistake on my side the move (not copy) constructor is not overloaded it is the default one 

`MachineBlockFrequencyInfo::MachineBlockFrequencyInfo(
    MachineBlockFrequencyInfo &&) = default;`

I think I should close this PR.


https://github.com/llvm/llvm-project/pull/101289