`ValueError: name is not a valid identifier: {k}`

[stijnh]

The following code is missing the f-prefix on the string, resulting in the error printing a literal {k}

https://github.com/KernelTuner/kernel_tuner/blob/b3ff4cdecb12655009b356e3b1840e25b1dd1421/kernel_tuner/util.py#L615