QiskitRuntimeService.getBackend should return BackendV2 (Adjust Type Hint)

[choerst-ibm]

What is the expected feature or enhancement?
Currently, using type hinting tooling with qiskit-ibm-runtime suggest a BackendV1 object is returned on a getBackend call.

qiskit-ibm-runtime/qiskit_ibm_runtime/qiskit_runtime_service.py

Line 23 in 88da374

from qiskit.providers.backend import BackendV1 as Backend

qiskit-ibm-runtime/qiskit_ibm_runtime/qiskit_runtime_service.py

Lines 817 to 821 in 88da374

	def backend(
	self,
	name: str = None,
	instance: Optional[str] = None,
	) -> Backend:

This should likely be changed to be BackendV2 by now so type hinting works nicely.