Missing f-string in logger warning

[keziah55]

In chaco/axis.py, PlotAxis._compute_tick_positions() the logger.warning message written if datalow > datahigh is using regular strings instead of f-strings, so the warning message is not formatted correctly.

It should be:

if datalow > datahigh:
    logger.warning(
        f"{self.mapper} has an invalid data range with "
        f"low={datalow} > high={datahigh}; unable to compute axis "
        "ticks."
    )