Reduce Email Alert API public limit to 50 requests a second
Reduce Email Alert API public limit to 50 requests a second

We've found in our tests on staging that we can start returning 502/504
responses with some of our testing. By lowering this to 50r/s we should
be a bit less close to cut off but still be able to handle 150r/s total
(which translates to 540,000 requests an hour).

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