[mtu-pr79-#80221576]: Update DEVELOPING.md
[mtu-pr79-#80221576]: Update DEVELOPING.md

 - take out extraenous colon
 - no need to build garden to test it

[#80118996]

cloudfoundry-incubator/garden-linux,shashidharatd/garden-linux,cloudfoundry-incubator/garden-linux,shashidharatd/garden-linux,shashidharatd/garden-linux,cloudfoundry-incubator/garden-linux,shashidharatd/garden-linux