Simplify if statement in element tables

[mscroggs]

This if statement has a complicated condition, made even more complicated by #836:

ffcx/ffcx/ir/elementtables.py

Lines 438 to 442 in 1dfd1a8

	if (
	integral_type == "interior_facet"
	or integral_type == "ridge"
	or (is_mixed_dim and codim == 0)
	):

We should look to see if the logic can be simplified.