[DOC]: `copy_n` docs formatting bug

### Is this a duplicate?

- [x] I confirmed there appear to be no [duplicate issues](https://github.com/NVIDIA/cccl/issues) for this bug and that I agree to the [Code of Conduct](CODE_OF_CONDUCT.md)

### Is this for new documentation, or an update to existing docs?

Update

### Describe the incorrect/future/missing documentation

https://github.com/NVIDIA/cccl/blob/deb90107357dd90ba10115dfd6cd8bf2831fce78/thrust/thrust/copy.h#L194
https://github.com/NVIDIA/cccl/blob/deb90107357dd90ba10115dfd6cd8bf2831fce78/thrust/thrust/copy.h#L100

The `+ \c i)` in the beginning of the line are treated as a back-quotes and ruin the formatting for the rest of the paragraph.

### If this is a correction, please provide a link to the incorrect documentation. If this is a new documentation request, please link to where you have looked.

https://nvidia.github.io/cccl/thrust/api/function_group__copying_1ga4eb33fdcfcf991eaf1c0ae209046922d.html
https://nvidia.github.io/cccl/thrust/api/function_group__copying_1gab3d33f1aa1d078b5f6b579f07313d058.html