ResNet-50 should be called ResNet-50 across all docs

[matthew-frank]

https://github.com/mlcommons/training/tree/master/object_detection#4-model uses the term "ResNet50" twice. We are trying to standardize terminology and usage across mlcommons. Please change these to "ResNet-50" (with a dash between ResNet and 50).

[johntran-nv]

@matthew-frank could you propose a PR to fix this?

[matthew-frank]

PR https://github.com/mlcommons/training/pull/603 is my proposed fix for the small amount of this problem that remains.

[hiwotadese]

Closing this issue because the benchmark is dropped for v4.1 and beyond.