Adding runtime limitation (#474)

* Adding runtime limitation

... see Codeception/Codeception#5359 (comment)
Question: Which other things (like `depends`) cannot be changed?

* Update docs/06-ModulesAndHelpers.md

Co-authored-by: Michael Bodnarchuk <DavertMik@users.noreply.github.com>

Author: ThomasLandauer

docs/06-ModulesAndHelpers.md

@@ -542,6 +542,8 @@ $this->getModule('WebDriver')->_restart();
 
 {% endhighlight %}
 
+> You cannot change static test configurations like `depends` at runtime.
+
 At the end of a test all configuration changes will be rolled back to the original configuration values.
 
 ### Runtime Configuration of a Test