layers: Fix compiler warning in ObjectTracker

Function validate_object should return VOID.
diff --git a/vk-layer-generate.py b/vk-layer-generate.py
index cadf8d5..215b246 100755
--- a/vk-layer-generate.py
+++ b/vk-layer-generate.py
@@ -870,7 +870,7 @@
         header_txt.append('}')
         header_txt.append('')
         header_txt.append('// Validate that object is in the object map')
-        header_txt.append('static bool32_t validate_object(const VkObject object)')
+        header_txt.append('static void validate_object(const VkObject object)')
         header_txt.append('{')
         header_txt.append('    if (objMap.find(object) == objMap.end()) {')
         header_txt.append('        char str[1024];')