Because (gnu packages golang) and (gnu packages check) use each other, this
avoids an undefined symbol due to a module dependency cycle.
* gnu/packages/check.scm (go-github-com-robfig-cron-1.2): Move to...
* gnu/packages/golang.scm (go-github-com-robfig-cron-1.2): ...here.
Signed-off-by: Tobias Geerinckx-Rice <me@tobias.gr>