fix out of date cli arg for registry version
@@ -108,7 +108,7 @@ directory. This includes formatting, vetting, linting, building,
testing and generating tagged binaries. We can verify this worked by running
the registry binary generated in the "./bin" directory:
- $ ./bin/registry -version
+ $ ./bin/registry --version
./bin/registry github.com/docker/distribution v2.0.0-alpha.2-80-g16d8b2c.m
### Optional build tags
