Fix compilation with recent Cython 3.x versions (#415)

Recent versions of Cython 3.x refuse to compile the
`_get_span2wp_alignment` function because it always requires acquiring
the GIL to check if any exceptions are raised. Change the function
signature to return an `int`, so that `-1` can be used to signal that
an exception occured.

It's not safe to qualify the function `noexcept`, since some calls can
throw an exception.

spacy_transformers/align.pyx

@@ -239,7 +239,7 @@ def get_span2wp_from_offset_mapping(span, wp_char_offsets):
     return result
 
 
-cdef void _get_span2wp_alignment(
+cdef int _get_span2wp_alignment(
         vector[unordered_set_uint32_t_ptr]* alignment,
         int32_t[::1] char_to_sp_token,
         int char_to_sp_token_length,
@@ -262,3 +262,4 @@ cdef void _get_span2wp_alignment(
                 deref(alignment.at(token_i)).insert(wp_j)
             char_idx += 1
         wp_j += 1
+    return 0