Fix RateLimiter binding name

[maxdeviant]

This PR fixes an issue where the RateLimiter could not be retrieved with Env::get_binding, as described in #700.

When trying to retrieve the rate limiter I was getting the following error:

Binding cannot be cast to the type RateLimiter from RateLimit

From what I can tell, the underlying issue is that the runtime constructor name is actually Ratelimit, based on this code here:

workers-rs/worker/src/env.rs

Line 123 in 38af58a

if obj.constructor().name() == Self::TYPE_NAME {

I was able to fix this by updating the type name from RateLimiter to Ratelimit in the EnvBinding impl.

If there is a different way this should be fixed, I am happy to pursue other avenues.