### Preflight Checklist

- [X] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
- [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
- [X] I have searched the [issue tracker](https://www.github.com/electron/electron/issues) for a feature request that matches the one I want to file, without success.

### Electron Version

12.0.1

### What operating system are you using?

macOS

### Operating System Version

11.2

### What arch are you using?

x64

### Last Known Working Electron version

_No response_

### Expected Behavior

`error.message` shouldn't be prefixed with "Uncaught Error:"

### Actual Behavior

`error.message` is prefixed with "Uncaught Error:" when an error is thrown in a function defined in the preload script and caught in the renderer process. This only happens when `contextIsolation` is enabled.

### Testcase Gist URL

https://gist.github.com/f11c77f9bc2cbf98d42a9fcaf477c80a


shell/renderer/api/electron_api_context_bridge.cc
if (try_catch.HasCaught()) {
        did_error = true;
        auto message = try_catch.Message();
        if (message.IsEmpty() ||
            !gin::ConvertFromV8(args.isolate(), message->Get(),
                                &error_message)) {
          error_message =
              "An unknown exception occurred in the isolated context, an error "
              "occurred but a valid exception was not thrown.";
        }
      }
    }
    if (did_error) {
      v8::Context::Scope calling_context_scope(calling_context);
      args.isolate()->ThrowException(
          v8::Exception::Error(gin::StringToV8(args.isolate(), error_message)));
      return;
    }
    if (maybe_return_value.IsEmpty())
      return;
    auto ret = PassValueToOtherContext(
        func_owning_context, calling_context,
        maybe_return_value.ToLocalChecked(), &object_cache,
        support_dynamic_properties, 0, BridgeErrorTarget::kDestination);
    if (ret.IsEmpty())
      return;
    info.GetReturnValue().Set(ret.ToLocalChecked());
  }
}
v8::MaybeLocal<v8::Object> CreateProxyForAPI(