Use fmt::format for LOGMESSAGE

The format string can be checked at compile time. It will be easier to
transition to `std::format`.

source/graphics/SkeletonAnimManager.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2025 Wildfire Games.
+/* Copyright (C) 2026 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -77,7 +77,10 @@ CSkeletonAnimDef* CSkeletonAnimManager::GetAnimation(const VfsPath& pathname)
 		}
 
 	if (def)
-		LOGMESSAGE("CSkeletonAnimManager::GetAnimation(%s): Loaded successfully", pathname.string8());
+	{
+		LOGMESSAGE("CSkeletonAnimManager::GetAnimation({}): Loaded successfully",
+			pathname.string8());
+	}
 	else
 		LOGERROR("CSkeletonAnimManager::GetAnimation(%s): Failed loading, marked file as bad", pathname.string8());