Fix flaky email tests (#19023)

Docstring for `regex-email-bodies` states:

> "Return messages in the fake inbox whose body matches the
regex(es). The body will be replaced by a map with the stringified regex
as it's key and a boolean indicated that the regex returned results."

But it does ont return messages in the fake inbox whose body matches any
of the regex. It returns them all regardless, with information if they
match or not. Simply correct this behavior to match the docstring

```clojure
{"rasta@metabase.com"
 ({:from "notifications@metabase.com",
   :to #{"rasta@metabase.com"},
   :subject "We've Noticed a New Metabase Login, Rasta",
   :body {"https://metabase.com/testmb" false, "has any results" false, "My question" false}}
  {:from "notifications@metabase.com",
   :to #{"rasta@metabase.com"},
   :subject "We've Noticed a New Metabase Login, Rasta",
   :body {"https://metabase.com/testmb" false, "has any results" false, "My question" false}}
  {:from "notifications@metabase.com",
   :to #{"rasta@metabase.com"},
   :subject "You set up an alert",
   :body {"https://metabase.com/testmb" true, "has any results" true, "My question" true}})}
```