Eliminates wrong preamble (for a method), closes #2799

doc/Type/Test.pod6

@@ -642,18 +642,16 @@ throws-like { EVAL q[ fac("foo") ] }, X::TypeCheck::Argument;
 
 Defined as:
 
-=for code :preamble<use Test;>
-
-sub fails-like ( \test where Callable:D|Str:D, $ex-type, $reason?, *%matcher)
+    sub fails-like ( \test where Callable:D|Str:D, $ex-type, $reason?, *%matcher)
 
 Same interface as C<throws-like>, except checks that the code returns a
 L<Failure|/type/Failure> instead of throwing. If the code does throw or if the
 returned L<Failure|/type/Failure> has already been L<handled|/routine/handled>,
 that will be considered as a failed test.
 
 =for code :preamble<use Test;>
-    fails-like { +"a" }, X::Str::Numeric,
-        :message(/'Cannot convert string to number'/),
+fails-like { +"a" }, X::Str::Numeric,
+    :message(/'Cannot convert string to number'/),
     'converting non-numeric string to number fails';
 
 =head2 sub subtest