Update SUMMARY.md

Author: Manishearth

src/SUMMARY.md

@@ -4,14 +4,14 @@
 - [Undefined behavior](./undefined_behavior.md)
 - [Core unsafety](./core_unsafety.md)
     - [Dangling and unaligned pointers](./core_unsafety/dangling_and_unaligned_pointers.md)
-    - [Invalid values](./core_unsafety/invalid_values.md)
     - [Data races](./core_unsafety/data_races.md)
     - [Intrinsics](./core_unsafety/intrinsics.md)
     - [ABI and FFI](./core_unsafety/abi_and_ffi.md)
     - [Platform features](./core_unsafety/platform_features.md)
     - [Inline assembly](./core_unsafety/inline_assembly.md)
 - [Advanced unsafety](./advanced_unsafety.md)
     - [Uninitialized memory](./advanced_unsafety/uninitialized.md)
+    - [Invalid values](./advanced_unsafety/invalid_values.md)
     - [Pointer aliasing](./advanced_unsafety/pointer_aliasing.md)
     - [Immutable data](./advanced_unsafety/immutable_data.md)
     - [Atomic ordering](./advanced_unsafety/atomic_ordering.md)