Give a mention in release notes

Author: Sayam753

RELEASE-NOTES.md

@@ -5,6 +5,7 @@
 + A deprecation warning from the `semver` package we use for checking backend compatibility was dealt with (see [#4547](https://github.com/pymc-devs/pymc3/pull/4547)).
 + `theano.printing.pydotprint` is now hotfixed upon import (see [#4594](https://github.com/pymc-devs/pymc3/pull/4594)).
 + Fix bug in the computation of the log pseudolikelihood values (SMC-ABC). (see [#4672](https://github.com/pymc-devs/pymc3/pull/4672)).
++ Fix `LKJCorr.random` method to work with `pm.sample_prior_predictive`. (see [#4780](https://github.com/pymc-devs/pymc3/pull/4780))
 
 ### New Features
 + Generalized BART, bounded distributions like Binomial and Poisson can now be used as likelihoods (see [#4675](https://github.com/pymc-devs/pymc3/pull/4675), [#4709](https://github.com/pymc-devs/pymc3/pull/4709) and