fixed broken links

Author: AloeareV

src/type-coercions.md

@@ -187,7 +187,7 @@ unsized coercion to `Foo<U>`.
 
 [RFC 401]: https://github.com/rust-lang/rfcs/blob/master/text/0401-coercions.md
 [RFC 1558]: https://github.com/rust-lang/rfcs/blob/master/text/1558-closure-to-fn-coercion.md
-[subtype]: subtyping.html`
-[as]: operator-expr.html#type-cast-expressions`
+[subtype]: subtyping.md`
+[as]: operator-expr.md#type-cast-expressions`
 [`Unsize`]: ../std/marker/trait.Unsize.html
 [`CoerceUnsized`]: ../std/ops/trait.CoerceUnsized.html