Remove usages of FullPath and SetFullPath RPCs
What does this MR do and why?
Contributes to #408940 (closed)
Problem
Gitaly plans to remove the SetFullPath and FullPath RPCs in the context of &8953 (closed). We need to adapt Rails to stop calling those RPCs so that we can move ahead with the planned removal.
Solution
Remove usages of FullPath and SetFullPath RPCs