Remove duplicated can_be_merged? method

lib/gitlab/git/repository.rb

@@ -1456,16 +1456,6 @@ module Gitlab
         output
       end
 
-      def can_be_merged?(source_sha, target_branch)
-        gitaly_migrate(:can_be_merged) do |is_enabled|
-          if is_enabled
-            gitaly_can_be_merged?(source_sha, find_branch(target_branch).target)
-          else
-            rugged_can_be_merged?(source_sha, target_branch)
-          end
-        end
-      end
-
       def last_commit_for_path(sha, path)
         gitaly_migrate(:last_commit_for_path) do |is_enabled|
           if is_enabled