cleanup fmt::format for std::format

Update the code to use std::format since gcc13 supports it now. Also
cleaned up some unused headers.

Change-Id: Ief2ad4df9e8b8227168f4f98213da8b3978fda03
Signed-off-by: Willy Tu <wltu@google.com>
diff --git a/subprojects/nemora-postd/meson.build b/subprojects/nemora-postd/meson.build
index b1c8921..21f8421 100644
--- a/subprojects/nemora-postd/meson.build
+++ b/subprojects/nemora-postd/meson.build
@@ -28,7 +28,6 @@
 sdbusplus = dependency('sdbusplus')
 threads = dependency('threads')
 logging = dependency('phosphor-logging')
-fmt = declare_dependency(compile_args: '-DFMT_STRING_ALIAS=1', dependencies: dependency('fmt'))
 
 protoc = find_program('protoc', native: true)
 
@@ -55,7 +54,7 @@
   'src/serializer.cpp',
   proto,
   include_directories: include_directories('.'),
-  dependencies: [protobuf, phosphor_dbus_interfaces, sdbusplus, threads, logging, fmt],
+  dependencies: [protobuf, phosphor_dbus_interfaces, sdbusplus, threads, logging],
   install: true
 )