syncval: Fix typo in usage doc

Correct small typo is synchronization usage documentation.

Change-Id: I0a744b164e7894a6211d95745e1e8bb4a3ddb386

Author: jzulauf-lunarg

docs/synchronization_usage.md

@@ -14,7 +14,7 @@
 
 Synchronization Validation (alpha release)
 
-Synchronization Validation is implemented in the `VK_LAYER_KHRONOS_validation layer`. When enabled, the Synchronization Object is intended to identify resource access conflicts due do missing or incorrect synchronization operations between actions (Draw, Copy, Dispatch, Blit) reading or writing the same regions of memory.
+Synchronization Validation is implemented in the `VK_LAYER_KHRONOS_validation layer`. When enabled, the Synchronization Object is intended to identify resource access conflicts due to missing or incorrect synchronization operations between actions (Draw, Copy, Dispatch, Blit) reading or writing the same regions of memory.
 
 Synchronization will ideally be run periodically after resolving any outstanding validation checks from all other validation objects, so that issues may be addressed in early stages of development.