Enable possibility to switch "compatible" repository types

Currently this is no more possible in Bamboo.

The only possibility of switchning respository types (e.g. raw Git to Bitbucket Server / Cloud and back) now is to additionally perform a build plan's repository update, as sketched below.

1. Create a new Linked repository (old repository type)
2. Create a new plan performing Source Code Checkout and build => checkout and build
3. Back to Overview >> Linked repositories: Deleted / rename the Linked repository of step 1
4. Create a new Linked repository with same / new name as previously deleted / renamed --> other repo type
5. Perform no update of build plan configuration >> Repositories tab: checkout and build use old repository / type
6. Delete and add new Linked repository >> Repositories tab: checkout and build (use new repository / type)

Please reenable this possibility without causing any issues with plan branches when doing so. The need to manually change plan configuration ia at least annoying.