Make fizz::ExtensionType compatible with fmt11

Summary:
starting from [fmt11.0.0](fmtlib/fmt#3447), fmt requires formatter::format to be const.
> Started enforcing that formatter::format is const for compatibility with std::format

X-link: facebookincubator/fizz#144

Reviewed By: NickR23

Differential Revision: D60912017

Pulled By: mingtaoy

fbshipit-source-id: 49e367c509a84523455220d791402ca4669942bd

third-party/fizz/src/fizz/record/Types.h

@@ -454,7 +454,7 @@ struct hash<fizz::ExtensionType> {
 
 template <>
 struct fmt::formatter<fizz::ExtensionType> : formatter<unsigned> {
-  auto format(fizz::ExtensionType t, format_context& ctx) {
+  auto format(fizz::ExtensionType t, format_context& ctx) const {
     return formatter<unsigned>::format(folly::to_underlying(t), ctx);
   }
 };