Specify signature of cmp-ok more accurately

- To indicate it can be used to test with `=:=` operator
- And that it doesn't interfere with ops that partly rely on
    address equivalency, such as `eqv`

Rakudo impl: rakudo/rakudo@3684384db1
Spec: Raku/roast@4bc442622d

Author: zoffixznet

doc/Language/testing.pod6

@@ -446,7 +446,7 @@ L«C<cmp-ok $got, 'eqv', $expected, $desc>|/language/testing#index-entry-cmp-ok-
 
 =head2 By arbitrary comparison
 
-=item X<cmp-ok($value, $comparison, $expected, $description?)|cmp-ok>
+=item X<cmp-ok(Mu $value is raw, $comparison, Mu $expected is raw, $description?)|cmp-ok>
 
 Compares C<$value> and C<$expected> with the given C<$comparison> comparator and
 passes the test if the comparison yields a C<True> value. The C<$description>