Consider setting MOZ_NORMANDY=False

I think since https://bugzilla.mozilla.org/show_bug.cgi?id=1569330 we need to set MOZ_NORMANDY=False in order to disable the "recipe runner" thing. I noticed that without this, on first run of a legacy/trac#33533 (moved) build there were a bunch of requests coming from the "recipe runner" module, which are gone after disabling Normandy. It seems it would need to be done similarly to legacy/trac#31457 (moved), by changing browser/moz.configure.