Expand one-liner python version check in _callback_num_args

Apparently some combination of python 3.11 and cython [0.29?] doesn't handle
the one-liner correctly, causing the `X` in `X if Y else Z` to be resolved even
when Y was False.

I (s0600204) never had this problem, hence the "apparently".

It could be that the users reporting the problem were using the release version
of 0.10.0, which doesn't have the one-liner, and thus always uses the defunct
`_inspect.getargspec`, causing the issue.

See also:
* dsacre#29
* Houston4444/RaySession#152 (comment)

src/liblo.pyx

@@ -277,8 +277,10 @@ cdef int _callback_num_args(func):
     """
     Return the number of arguments that should be passed to callback *func*.
     """
-    getargspec = (_inspect.getargspec if PY_VERSION_HEX < 0x03000000
-             else _inspect.getfullargspec)
+    if PY_VERSION_HEX < 0x03000000:
+        getargspec = _inspect.getargspec
+    else:
+        getargspec = _inspect.getfullargspec
 
     if isinstance(func, _functools.partial):
         # before Python 3.4, getargspec() did't work for functools.partial,