Remove redundant sentence

Author: jruderman

Diff for: compiler/rustc_error_codes/src/error_codes/E0210.md

@@ -76,7 +76,5 @@ Let `Ti` be the first such type.
 For information on the design of the orphan rules,
 see [RFC 2451] and [RFC 1023].
 
-For information on the design of the orphan rules, see [RFC 1023].
-
 [RFC 2451]: https://rust-lang.github.io/rfcs/2451-re-rebalancing-coherence.html
 [RFC 1023]: https://github.com/rust-lang/rfcs/blob/master/text/1023-rebalancing-coherence.md