There is no class named QuantumKernel, hence the error.

See the API ref https://qiskit-community.github.io/qiskit-machine-learning/apidocs/qiskit_machine_learning.kernels.html#module-qiskit_machine_learning.kernels for the classes that are there.

Also see the tutorials such as this one for quantum kernels https://qiskit-community.github.io/qiskit-machine-learning/tutorials/03_quantum_kernel.html