message: fix build error docs
diff: @@ -99,7 +99,7 @@ pub fn call_protected<T>(
  Ok(SIGSEGV) | Ok(SIGBUS) => WasmTrapInfo::MemoryOutOfBounds,
  Ok(SIGFPE) => WasmTrapInfo::IllegalArithmetic,
  _ => unimplemented!(
  - "WasmTrapInfo::Unknown signal:{}",
  + "WasmTrapInfo::Unknown signal:{:?}",
  Signal::from_c_int(signum)
  ),
  }))
  