Fix a typo in a test function

[eerovaher]

One of the things that happens when pyerfa is built is that the tests in t_erfa_c.c are converted into pytest tests, but an extraneous whitespace in a single line is needlessly complicating that conversion because that line cannot be processed by calling line.removeprefix("viv(") in Python.

[mhvk]

@eerovaher - this is a nice idea, but a problem is that these .c files are direct renames from the corresponding sofa files, so any edits have to be propagated every time SOFA updates its test file. I think it may be better to just do a .replace("viv (", "viv(") or so... Possibly, this can in fact be done in the script that does the renaming...