Dvc: typo in docs

[siddygups]

super minor typo:

$dvc repro --help
-c CWD, --cwd CWD Directory within your repo to reroduce from.

dvc --version
0.30.1

[shcheklein]

@siddygups hi! thanks! could create a PR? You don't need to setup any environment for this - just open the https://github.com/iterative/dvc/blob/master/dvc/command/repro.py#L62 and click an edit button at the very top. You can edit right in-place and then create a PR :)

[siddygups]

sorry I missed this - lemme know if there is something else I can look into

[shcheklein]

@siddygups np! Almost any of these should be easy enough https://github.com/iterative/dvc/labels/good%20first%20issue. Would be really great if could contribute one of them. Any help is great! :)