Tweak test to work even when we find error at compile time

The test assumes the dispatch failure will only ever going to
be detected at runtime, but we're now smart enough to detect
it at compile time.

Fix the test by using eval-dies-ok instead of just dies-ok.

S06-signature/unspecified.t

@@ -29,7 +29,7 @@ is &named.signature.perl, ':(*%_)',
    'signature is :(Mu *%_) when none is specified and %_ is used, RT #125486';
 is named( :bravo<charlie> ), 'charlie', 'can call sub with named param used';
 nok named().defined, 'named param sub is callable with no params';
-dies-ok { named( 'zulu' ) }, 'named param sub dies with positional param';
+eval-dies-ok ｢named( 'zulu' )｣, 'named param sub dies with positional param';
 
 sub both { @_[1] ~ %_<delta> }
 is &both.signature.perl, ':(*@_, *%_)',