update docs on NsightCompute profiling with / in syntax

[baperry2]

Summary

Documentation on using NsightCompute to profile kernels in AMReX codes needs to be updated to include a "/" at the end of the desired TinyProfiler name because TinyProfiler uses Push/Pop NVTX regions.

Additional background

https://docs.nvidia.com/nsight-compute/NsightComputeCli/index.html#nvtx-filtering

Checklist

The proposed changes:

• fix a bug or incorrect behavior in AMReX
• add new capabilities to AMReX
• changes answers in the test suite to more than roundoff level
• are likely to significantly affect the results of downstream AMReX users
• include documentation in the code and/or rst files, if appropriate