Remove link from List Raku#3841

This is another false link that probably needs removing.
There is no `routine_Str`or `method_Str` documented in `Any`. I could not find a single reference to `.Str` that I could replace the reference with.
Removing the link does not seem to me to be important, but it probably should be an issue that `Str` is not documented in a single place. Strings and stringification are important enough to need a separate document.

doc/Type/List.pod6

@@ -344,7 +344,7 @@ Defined as:
     method join(List:D: $separator = "")
 
 Treats the elements of the list as strings by calling
-L<C<.Str>|/type/Any#routine_Str> on each of them, interleaves them with
+C<.Str> on each of them, interleaves them with
 C<$separator> and concatenates everything into a single string.
 
 Example: