DOC fix parameter name in CoordinateTransform.reverse docstring

[eeshsaxena]

The reverse method of CoordinateTransform documents parameter labels but the actual signature uses coord_labels:

def reverse(self, coord_labels: dict[Hashable, Any]) -> dict[str, Any]:
    """
    labels : dict   # <-- wrong: should be coord_labels
    """

One-line docstring fix.

[welcome]

Thank you for opening this pull request! It may take us a few days to respond here, so thank you for being patient.
If you have questions, some answers may be found in our contributing guidelines.