Remove diagnostics from switch to window tests

t/10-switch-to-window.t

@@ -47,7 +47,6 @@ my $handles = $s->get_window_handles;
 is scalar(@$handles), 2;
 # We don't assume any order in the @$handles array:
 my $cpan_handle = $perl_handle eq $handles->[0] ? $handles->[1] : $handles->[0];
-diag explain $handles;
 
 $s->switch_to_window($cpan_handle);
 $s->title_is($cpan_title);