update release notes

Author: katosh

RELEASE-NOTES.md

@@ -6,14 +6,14 @@
 - Mentioned the way to do any random walk with `theano.tensor.cumsum()` in `GaussianRandomWalk` docstrings (see [#4048](https://github.com/pymc-devs/pymc3/pull/4048)).
 - Fixed numerical instability in ExGaussian's logp by preventing `logpow` from returning `-inf` (see [#4050](https://github.com/pymc-devs/pymc3/pull/4050)).
 - Use dill to serialize user defined logp functions in `DensityDist`. The previous serialization code fails if it is used in notebooks on Windows and Mac. `dill` is now a required dependency. (see [#3844](https://github.com/pymc-devs/pymc3/issues/3844)).
+- Numerically improved stickbreaking transformation - e.g. for the `Dirichlet` distribution. [#4129](https://github.com/pymc-devs/pymc3/pull/4129)
 
 ### Documentation
 
 ### New features
 - `sample_posterior_predictive_w` can now feed on `xarray.Dataset` - e.g. from `InferenceData.posterior`. (see [#4042](https://github.com/pymc-devs/pymc3/pull/4042))
 - Add MLDA, a new stepper for multilevel sampling. MLDA can be used when a hierarchy of approximate posteriors of varying accuracy is available, offering improved sampling efficiency especially in high-dimensional problems and/or where gradients are not available (see [#3926](https://github.com/pymc-devs/pymc3/pull/3926))
 - Change SMC metropolis kernel to independent metropolis kernel [#4115](https://github.com/pymc-devs/pymc3/pull/3926))
-- Alternative transformation of the simplex `StickBreaking2` - e.g. for the `Dirichlet` distribution. [#4129](https://github.com/pymc-devs/pymc3/pull/4129)
 
 
 ## PyMC3 3.9.3 (11 August 2020)