Reinstate original grep handler for junctions

The new Seq based code for some reason does not handle grepping using with
a junction (at least according to test 28 in S32-list/grep.t).  Adding this
candidate using the original code, makes the test pass.  Not 100% if that
test is legit, though.  At least this reinstates the previous behaviour.

src/core/Any-iterable-methods.pm

@@ -356,6 +356,9 @@ augment class Any {
             self.map(&tester);
         }
     }
+    multi method grep(Junction $test) is rw {
+        self.map({ next unless $_ ~~ $test; $_ });
+    }
     multi method grep(Mu $test) is rw {
         Seq.new(class :: does Grepper {
             method pull-one() is rw {