normalize_number fails on exponent / fractional input

[evanmiller-anthropic]

With input such as 1², this conditional returns true:

inspect_ai/src/inspect_ai/scorer/_common.py

Line 98 in f2fa3b6

if number.replace(".", "").isnumeric():

but the next line fails with ValueError: could not convert string to float: '1²'

inspect_ai/src/inspect_ai/scorer/_common.py

Line 99 in f2fa3b6

num = float(number)