on_post_birth effect doesn't work for Bretons.

[Nendur]

In 01_ek_on_actions.txt, the on_post_birth effect detects Bretons using celticgfx instead of frankishgfx.
A simple and flexible replacement for the fixed cultures would be:

         	random_list = {
			40 = { #Father's race
				true_father_even_if_dead = {
					gfx_culture_scope = {
						ROOT = {
							set_graphical_culture = PREV
						}
					}
				}
			}
			60 = { #Mother's race
				mother_even_if_dead = {
					gfx_culture_scope = {
						ROOT = {
							set_graphical_culture = PREV
						}
					}
				}
			}
		}