TRPL editing: move patterns back

We want to talk about how to pattern match on structs, so let's bump
it back one.

Author: steveklabnik

src/doc/trpl/SUMMARY.md

@@ -30,8 +30,8 @@
     * [Move semantics](move-semantics.md)
     * [Enums](enums.md)
     * [Match](match.md)
-    * [Patterns](patterns.md)
     * [Structs](structs.md)
+    * [Patterns](patterns.md)
     * [Method Syntax](method-syntax.md)
     * [Drop](drop.md)
     * [Vectors](vectors.md)