Add return keyword

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: simsurace

src/chainrules.jl

@@ -209,7 +209,7 @@ function ChainRulesCore.rrule(
             x̄[:, i] += ds
             ȳ[:, i] -= ds
         end
-        NoTangent(), (r=r̄,), @thunk(project_x(x̄)), @thunk(project_y(ȳ))
+        return NoTangent(), (r=r̄,), @thunk(project_x(x̄)), @thunk(project_y(ȳ))
     end
     return Distances.colwise(d, x, y), colwise_pullback
 end