wasmtime: Rip out incomplete/incorrect externref "host info" support

Better to be loud that we don't support attaching arbitrary host info to
`externref`s than to limp along and pretend we do support it. Supporting it
properly won't reuse any of this code anyways.

crates/c-api/src/memory.rs

@@ -37,7 +37,7 @@ pub extern "C" fn wasm_memory_new(
     store: &wasm_store_t,
     mt: &wasm_memorytype_t,
 ) -> Box<wasm_memory_t> {
-    let memory = HostRef::new(&store.store, Memory::new(&store.store, mt.ty().ty.clone()));
+    let memory = HostRef::new(Memory::new(&store.store, mt.ty().ty.clone()));
     Box::new(wasm_memory_t {
         ext: wasm_extern_t {
             which: ExternHost::Memory(memory),