layers: Simplified CastFromHandle argument deduction

By putting the return value as the first template arguement, only the
first argument is needed typically (the second can be deduced).

Change-Id: I4d0900bc03980f856c0c3bec87ab7eb1bd98aa44
diff --git a/layers/shader_validation.cpp b/layers/shader_validation.cpp
index 3482a18..9292c33 100644
--- a/layers/shader_validation.cpp
+++ b/layers/shader_validation.cpp
@@ -2534,7 +2534,7 @@
 static ValidationCache *GetValidationCacheInfo(VkShaderModuleCreateInfo const *pCreateInfo) {
     const auto validation_cache_ci = lvl_find_in_chain<VkShaderModuleValidationCacheCreateInfoEXT>(pCreateInfo->pNext);
     if (validation_cache_ci) {
-        return CastFromHandle<VkValidationCacheEXT, ValidationCache *>(validation_cache_ci->validationCache);
+        return CastFromHandle<ValidationCache *>(validation_cache_ci->validationCache);
     }
     return nullptr;
 }