FRA-NOR A13 exit numbers

[neroute2]

These seem to have changed near the west end:
29a -> 29
29b -> 30
30 -> 31
31 -> no longer numbered? I see signs for D403 and D675 at the interchange, but nothing for N814

[michih]

https://github.com/TravelMapping/HighwayData/pull/6729

I replaced "31" by "N814" though since it is the official number albeit the route is called "Périphérique" all over the place.
I'm gone with "31a" for A13 since "31" is in use by some 10 users.