PEL: switch fmt::format to use std::format

fmt::format is supported in the c++ std. This will
    help to remove fmt package dependency.

Change-Id: I89f0a5b67bbfe54168a20e93c989a1ae87f54503
Signed-off-by: Jayanth Othayoth <ojayanth@in.ibm.com>
diff --git a/extensions/openpower-pels/extended_user_data.cpp b/extensions/openpower-pels/extended_user_data.cpp
index 6ff394a..441993a 100644
--- a/extensions/openpower-pels/extended_user_data.cpp
+++ b/extensions/openpower-pels/extended_user_data.cpp
@@ -19,10 +19,10 @@
 #ifdef PELTOOL
 #include "user_data_json.hpp"
 #endif
-#include <fmt/format.h>
-
 #include <phosphor-logging/log.hpp>
 
+#include <format>
+
 namespace openpower::pels
 {
 
@@ -35,7 +35,7 @@
     if (_header.size <= SectionHeader::flattenedSize() + 4)
     {
         throw std::out_of_range(
-            fmt::format("ExtendedUserData::unflatten: SectionHeader::size {} "
+            std::format("ExtendedUserData::unflatten: SectionHeader::size {} "
                         "too small",
                         _header.size));
     }
@@ -61,7 +61,7 @@
     catch (const std::exception& e)
     {
         log<level::ERR>(
-            fmt::format("Cannot unflatten ExtendedUserData section: {}",
+            std::format("Cannot unflatten ExtendedUserData section: {}",
                         e.what())
                 .c_str());
         _valid = false;
@@ -90,7 +90,7 @@
     if (header().id != static_cast<uint16_t>(SectionID::extUserData))
     {
         log<level::ERR>(
-            fmt::format("Invalid ExtendedUserData section ID: {0:#x}",
+            std::format("Invalid ExtendedUserData section ID: {0:#x}",
                         header().id)
                 .c_str());
         _valid = false;