Fix warnings due to unused 'map' param on map_free on upb kernel (where the upb_free function is a no-op)

PiperOrigin-RevId: 615535675

src/google/protobuf/compiler/rust/enum.cc

@@ -177,7 +177,7 @@ void EnumProxiedInMapValue(Context& ctx, const EnumDescriptor& desc) {
                   $pbr$::InnerMap::new($pbi$::Private, raw, arena))
           }
 
-          unsafe fn map_free(_private: $pbi$::Private, map: &mut $pb$::Map<$key_t$, Self>) {
+          unsafe fn map_free(_private: $pbi$::Private, _map: &mut $pb$::Map<$key_t$, Self>) {
               // No-op: the memory will be dropped by the arena.
           }
 

src/google/protobuf/compiler/rust/message.cc

@@ -597,7 +597,7 @@ void MessageProxiedInMapValue(Context& ctx, const Descriptor& msg) {
                         $pbr$::InnerMap::new($pbi$::Private, raw, arena))
                 }
 
-                unsafe fn map_free(_private: $pbi$::Private, map: &mut $pb$::Map<$key_t$, Self>) {
+                unsafe fn map_free(_private: $pbi$::Private, _map: &mut $pb$::Map<$key_t$, Self>) {
                     // No-op: the memory will be dropped by the arena.
                 }