Merge #1752

1752: Clarify that `params` updates r=ToucheSir a=KronosTheLate

I was confused when initally reading the overciew, because I though that `params` returned a tuple of vectors. I see now that the printing of `parameters` reveals the output to be something else, but I think it is relevant what a less experienced programmer may read it as. It later becomes apparent that it actually returns another data-structure, because it updates when parameters change. I have added a single sentence to clarify this point. Edits on the wording/phrasing are very welcome.

Co-authored-by: KronosTheLate <61620837+KronosTheLate@users.noreply.github.com>

Author: bors[bot]

docs/src/models/overview.md

@@ -117,7 +117,7 @@ julia> parameters = Flux.params(predict)
 Params([[-0.99009055], [0.0]])
 ```
 
-These are the parameters Flux will change, one step at a time, to improve predictions. Each of the parameters comes from the `predict` model: 
+These are the parameters Flux will change, one step at a time, to improve predictions. At each step, the contents of this `Params` object changes too, since it is just a collection of references to the mutable arrays inside the model: 
 
 ```
 julia> predict.weight in parameters, predict.bias in parameters