Dvc: Fix dvc -h usage for `dvc gc`

[kurianbenoy]

Please provide information about your setup
DVC version: 0.41.3
Someone should add usage for dvc status -R option

context
-https://github.com/iterative/dvc.org/pull/396#discussion_r292251163

[jorgeorpinel]

In fact most cmd refs need to be checked for updated usage blocks...

[kurianbenoy]

Some other commands, when I checked command reference are:
dvc status , metrics, remove

[efiop]

There is no -R for gc, where did you get it from @kurianbenoy ?

[kurianbenoy]

dvc metrics -R doesn't seem to be defined

[efiop]

@kurianbenoy dvc metrics show -R is though.

[kurianbenoy]

Ok

[efiop]

Closing. -R in metrics is also documented.