katcp.Message.format_argument parser doesnt handle numpy float correctly

[sr-cdf]

Passing np.float32 type such as np.float32(0.0) gives b'np.float32(0.0)' instead of b'0.0'.

Casting to python float before generating the printable representation fixes this for me:

katcp-python/katcp/core.py

Lines 316 to 317 in 7a94c7d

	elif isinstance(arg, numbers.Real):
	return repr(arg).encode('ascii')

        elif isinstance(arg, numbers.Real):
            return repr(float(arg)).encode('ascii')

This was on RFSoC ARM with Ubuntu 24.04.03, Python 3.12.3, Numpy 2.4.3 and katcp 0.9.3.