Replace HetznerBareMetalHost "update" call with "patch" to avoid conflict errors

[janiskemper]

/kind bug

What steps did you take and what happened:
We observed, that having a conflict error while deprovisioning a HetznerBareMetalHost is very common, as the HetznerBareMetalMachine controller also updates it. This lead to situations, usually under heavy load, where the object completely stopped reconciling.

It is weird that this happened and not really the fault of our "requeue" mechanism, but still, we could avoid this altogether, if we manage to get rid of "update".

What did you expect to happen:
We can avoid errors that lead to the HetznerBareMetalHost reconciling multiple times in the same state, or even stopping to reconcile at all, if we use the patch logic.

Anything else you would like to add:
I don't remember why we used "update" instead of "patch". There was a reason. That reason might be irrelevant by now, as we took this decision years ago. We should still ensure that we don't run into problems.