PEL: Removed unused includes

The clangd LSP indicates when includes aren't used directly.

Tested:
Unit tests pass.

Change-Id: I8290fe59abd1cef4fada27aeb5adb2c45c289abb
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/test/openpower-pels/json_utils_test.cpp b/test/openpower-pels/json_utils_test.cpp
index 5a3d1a1..92b9990 100644
--- a/test/openpower-pels/json_utils_test.cpp
+++ b/test/openpower-pels/json_utils_test.cpp
@@ -19,6 +19,7 @@
 #include <nlohmann/json.hpp>
 
 #include <filesystem>
+#include <fstream>
 
 #include <gtest/gtest.h>