Update exposed-effects.md
Update exposed-effects.md

According to the documentation there is a method available called `asEffect` available from the `redux-saga/utils` package - see here for more (Inspect Specific Properties): http://redux-saga-test-plan.jeremyfairbank.com/integration-testing/exposed-effects.html

This is no longer available from as the  `redux-saga/utils` package no longer exists. (https://github.com/redux-saga/redux-saga/issues/2145)

Not an issue for testing as you can still just inspect the `effects` object returned.
jfairbank/redux-saga-test-plan