docs: Update to correct SyncVal Guide URL

Update the URL to the corrected version.

Change-Id: I8fac421bbca79dcac49ff336ef2d26d0b57deb98
diff --git a/docs/synchronization_usage.md b/docs/synchronization_usage.md
index 46acf21..18bfd69 100644
--- a/docs/synchronization_usage.md
+++ b/docs/synchronization_usage.md
@@ -242,5 +242,5 @@
 
 Yet another blog explaining Vulkan synchronization[ http://themaister.net/blog/2019/08/14/yet-another-blog-explaining-vulkan-synchronization/](http://themaister.net/blog/2019/08/14/yet-another-blog-explaining-vulkan-synchronization/)
 
-A Guide to Vulkan Synchronization Validation https://www.lunarg.com/wp-content/uploads/2021/01/Final_Guide-to-Vulkan-Synchronization-Validation_01_21.pdf
+A Guide to Vulkan Synchronization Validation https://www.lunarg.com/wp-content/uploads/2021/01/Final_Guide-to-Vulkan-Synchronization-Validation_Jan_21.pdf