core: Reduce unused includes

src/core/crypto/key_manager.h

@@ -5,7 +5,6 @@
 #pragma once
 
 #include <array>
-#include <filesystem>
 #include <map>
 #include <optional>
 #include <string>
@@ -16,6 +15,10 @@
 #include "common/common_types.h"
 #include "core/crypto/partition_data_manager.h"
 
+namespace std::filesystem {
+class path;
+}
+
 namespace Common::FS {
 class IOFile;
 }