wasi: get rid of missing_memory config

crates/wasi/src/lib.rs

@@ -33,8 +33,6 @@ resolution.",
           }
         },
     },
-    // Error to return when caller module is missing memory export:
-    missing_memory: { wasi_common::wasi::types::Errno::Inval },
 });
 
 pub fn is_wasi_module(name: &str) -> bool {