Mention SMC/named models related PR pymc-devs#4365

RELEASE-NOTES.md

@@ -33,6 +33,7 @@ It also brings some dreadfully awaited fixes, so be sure to go through the chang
 - Fixed `MatrixNormal` random method to work with parameters as random variables. (see [#4368](https://github.com/pymc-devs/pymc3/pull/4368))
 - Update the `logcdf` method of several continuous distributions to return -inf for invalid parameters and values, and raise an informative error when multiple values cannot be evaluated in a single call. (see [4393](https://github.com/pymc-devs/pymc3/pull/4393))
 - Improve numerical stability in `logp` and `logcdf` methods of `ExGaussian` (see [#4407](https://github.com/pymc-devs/pymc3/pull/4407))
+- Attempting to sample a named model with SMC will now raise a `NotImplementedError`. (see [#4365](https://github.com/pymc-devs/pymc3/pull/4365))
 
 ## PyMC3 3.10.0 (7 December 2020)