Auto-format code with black (#706)

Co-authored-by: explosion-bot <explosion-bot@users.noreply.github.com>

Author: github-actions[bot]

thinc/backends/_custom_kernels.py

@@ -171,9 +171,13 @@ def clipped_linear(
 
 def gather_add(table, indices, *, threads_per_block=128, num_blocks=128):
     if table.ndim != 2:
-        raise ValueError(f"gather_add expects table with dimensionality 2, was: {table.ndim}")
+        raise ValueError(
+            f"gather_add expects table with dimensionality 2, was: {table.ndim}"
+        )
     if indices.ndim != 2:
-        raise ValueError(f"gather_add expects indices with dimensionality 2, was: {indices.ndim}")
+        raise ValueError(
+            f"gather_add expects indices with dimensionality 2, was: {indices.ndim}"
+        )
     _is_float_array(table)
     indices = indices.astype("int32")
     _check_indices(indices, table.shape[0])