Link to dependent branch list doesn't work

[Martin von Gagern]

In https://code.launchpad.net/~gagern/bzr/bug560030-include-bash-completion-plugin I've got a merge request, and there is currently one other merge request depending on this one, https://code.launchpad.net/~gagern/bzr/bash_completion-ExecutableFeature/+merge/24951 . As a consequence, the "Branch merges" section correctly states "1 branch dependent on this one." However, the text "1 branch" is a link to the list of requests for merging into that branch, which doesn't include the dependent branch. So the link should point to a list generated using the "Prerequisite" property of merge requests, not the "Merge into" property.