[5.5] make fluent Route::middleware work with variadic arguments

[themsaid]

Currently:

Route::get('two', function () {
            return 'Hello World';
})->middleware(Middleware::class, Middleware2::class);

Middleware2 will run, but if you do this it won't:

Route::middleware(Middleware::class, Middleware2::class)
    ->get('one', function () {
                return 'Hello World';
});
``

This PR fixes that.