bug #112 Fix Symfony 5.x deprecation message by adding return type. (…

…Housik)

This PR was merged into the main branch.

Discussion
----------

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | fixed
| Fixed tickets | no ticket
| License       | MIT



Commits
-------

7ecb367 Fix Symfony deprecation message by adding return type.

src/DependencyInjection/Configuration.php

@@ -16,7 +16,7 @@
 
 class Configuration implements ConfigurationInterface
 {
-    public function getConfigTreeBuilder()
+    public function getConfigTreeBuilder(): TreeBuilder
     {
         $treeBuilder = new TreeBuilder('rollerworks_password_strength');