minor errors and ambiguities in docs

[mmvandieren]

CPU should be GPU on the note in documentation before the Run section: https://nvidia.github.io/cuda-quantum/latest/using/basics/run_kernel.html

kernel(thetas) syntax is used twice on the docs page: https://nvidia.github.io/cuda-quantum/latest/using/examples/building_kernels.html

this syntax doesn't initiate an error, but also doesn't do anything. So I'm not sure we should be giving this as an example in the docs

Fixed with PR #3383