cmd ref: remove prereq sentence from get --rev option

per #936 (review)

Author: jorgeorpinel

public/static/docs/command-reference/get.md

@@ -58,8 +58,7 @@ name.
   an existing directory is specified, then the output will be placed inside of
   it.
 
-- `--rev` - `url` is expected to contain a Git repository for this option to
-  have an effect. Specific
+- `--rev` - specific
   [Git revision](https://git-scm.com/book/en/v2/Git-Internals-Git-References)
   (such as a branch name, a tag, or a commit hash) of the repository to download
   the file or directory from. The tip of the default branch is used by default