feat: raise ValueError for mixed indices

This changes #1305

src/awkward/_v2/_slicing.py

@@ -49,8 +49,10 @@ def getitem_broadcast(items):
 
     if awkward_items > 1 or (awkward_items == 1 and len(broadcastable) != 0):
         raise ak._v2._util.error(
-            TypeError(
-                "cannot mix Awkward slicing (using an array with missing or variable-length lists in the slice) with NumPy advanced slicing (using more than one broadcastable array or integer in the slice), though you can perform multiple slices"
+            ValueError(
+                "cannot mix Awkward slicing (using an array with missing or variable-length lists in the slice) with "
+                "NumPy advanced slicing (using more than one broadcastable array or integer in the slice), "
+                "though you can perform multiple slices "
             )
         )
 

tests/v2/test_1305-mixed-awkward-numpy-slicing.py

@@ -9,5 +9,5 @@ def test():
     array = ak._v2.Array([[3.14]])
     first_slice = ak._v2.Array([True, None])[:1]  # type is 1 * ?bool
     second_slice = 0
-    with pytest.raises(TypeError):
+    with pytest.raises(ValueError):
         array[first_slice, second_slice]