Placeholder color in Select component not as expected.

[morrisseybr]

While I was using the form components, I noticed that the default for the placeholder in the Select component is not the same as the Input.

Looking at the code I realized that the intention was for the placeholder of the Select to be the color "text-muted-foreground" like the one of the Input, however, the class placeholder:text-muted-foreground was used, but in the Radix UI documentation it says to use the data-placeholder attribute to style this component and, by doing so, it returns to the expected behavior.

I will make a PR correcting this detail and submit it for evaluation. I apologize if this is not the usual contribution process. I've been working in the area for a few years, but this is the first time I've tried to contribute to a project. I will be very grateful if I receive constructive feedback.