Doxygen comments for in/out parameters should be in,out

[ChuckHastings]

Noticed while looking at a CI error that there were warnings in the cugraph Doxygen code generation.

We specify parameters that are used as input and modified during the function (e.g. the rng_state variable) using the annotation: @param [in/out].

These are generating warnings. According to the doxygen documentation here we should be using the annotation @param [in,out].