remove duplicate word

Author: coke

doc/Type/Date.pod6

@@ -168,7 +168,7 @@ Defined as:
 
     multi method Str(Date:D: --> Str:D)
 
-Returns a string representation of the invocant, as specified by the
+Returns a string representation of the invocant, as specified by
 L<the formatter|/type/Dateish#method_formatter>. If no formatter was
 specified, an (L<ISO 8601|https://en.wikipedia.org/wiki/ISO_8601>) date
 will be returned.