use std::format instead of fmt::format

The std::format is sufficient for the uses in this repository except
for in one file (override_fan_target.cpp, since P2286 isn't supported
by GCC yet).  Switch to std::format whenever possible.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ib2576fb530a4d7ce238e1b0bd95b40b476ec2107
diff --git a/presence/fallback.cpp b/presence/fallback.cpp
index a3c5e72..f301ac1 100644
--- a/presence/fallback.cpp
+++ b/presence/fallback.cpp
@@ -18,11 +18,10 @@
 #include "fan.hpp"
 #include "psensor.hpp"
 
-#include <fmt/format.h>
-
 #include <phosphor-logging/log.hpp>
 
 #include <algorithm>
+#include <format>
 
 namespace phosphor
 {
@@ -54,7 +53,7 @@
                 ++activeSensor;
             }
             phosphor::logging::log<phosphor::logging::level::INFO>(
-                fmt::format("Using backup presence sensor for fan {}",
+                std::format("Using backup presence sensor for fan {}",
                             std::get<1>(fan))
                     .c_str());
             activeSensor = it;
@@ -92,7 +91,7 @@
     if (activeSensor != sensors.begin())
     {
         phosphor::logging::log<phosphor::logging::level::INFO>(
-            fmt::format("Using backup presence sensor for fan {}",
+            std::format("Using backup presence sensor for fan {}",
                         std::get<1>(fan))
                 .c_str());
     }