Clean up 404 routes that we don't need anymore

[kumar303]

Fixes mozilla/addons#10270

[kumar303]

@muffinresearch re: mozilla/addons#10266 ...

I'll add comments to the routes to make it clear that ops need to be told when new routes are added.

Did that comment ever get added? Should I add it?

[muffinresearch]

Did that comment ever get added? Should I add it?

Oops, I think that slipped through the net. Good catch - please do.

[muffinresearch]

Since it doesn't matter leaving these, would it be worth folding this into the react-router upgrade to avoid having any weird falling-through locally?

[muffinresearch]

r+wc

[kumar303]

would it be worth folding this into the react-router upgrade to avoid having any weird falling-through locally?

I think it's ok to do the two patches independently. The lack of 404 routes will cause a 500 locally which isn't really any more or less helpful than a 404.