Fix some problems with async rendering

[brianush1]

• Fixed typo (if (e.async)) that lead to the Or, if you meant to create an async function, pass async: true as an option. message always being shown regardless of the async option.
• Fixed problem in the __express function where a raw Promise was being passed to express.js when async was enabled, instead of waiting on the Promise to resolve and passing the result to express.

Edit: If anyone is having this problem and would like to fix it, until this gets merged, use:

ejs.__express = (file, options, callback) => {
	if (options.async) {
		ejs.renderFile(file, options, async (err, promise) => {
			callback(err, await promise);
		});
	}
	else {
		ejs.renderFile(file, options, callback);
	}
}

[ExE-Boss]

I already fixed this in #460 (d6376fa).

[mde]

As @ExE-Boss noted, this is already fixed.