Make spelling of HPC consistent throughout documentation

[b-reyes]

Throughout our documentation we use High Performance Computing, High-performance computing, and High-Performance Computing. As a team we have decided to go with High-Performance Computing. We need to go through all of our documentation and make sure we are consistent with this spelling.

[b-reyes]

Be sure to put this on the contributing to CURC docs page: https://curc.readthedocs.io/en/latest/additional-resources/contrib_curc_docs.html