Clarify effects of IterationSetup on UnrollFactor and InvocationCount (#1776)

As mentioned in #730 (comment)

Author: SnakyBeaky

docs/articles/samples/IntroSetupCleanupIteration.md

@@ -5,7 +5,7 @@ uid: BenchmarkDotNet.Samples.IntroSetupCleanupIteration
 ## Sample: IntroSetupCleanupIteration
 
 A method which is marked by the [`[IterationSetup]`](xref:BenchmarkDotNet.Attributes.IterationSetupAttribute)
-  attribute will be executed exactly once *before each benchmark invocation* (we have changed that in 0.11.0).
+  attribute will be executed exactly once *before each benchmark invocation*, forcing `UnrollFactor=1` and `InvocationCount=1` (we have changed that in 0.11.0).
 It's not recommended to use this attribute in microbenchmarks because it can spoil the results.
 However, if you are writing a macrobenchmark (e.g. a benchmark which takes at least 100ms) and
   you want to prepare some data before each invocation,