Merge branch '4.1'

* 4.1:
  [travis] cache composer.lock files for deps=low
  [Security] Remove wrong sentence about ACL
  Update validators.nl.xlf
  [Routing] Fixed scheme redirecting for root path
  [Form] Remove extra .form-group wrapper around file widget in bootstrap 4

Author: nicolas-grekas

Resources/translations/validators.nl.xlf

@@ -316,7 +316,7 @@
             </trans-unit>
             <trans-unit id="83">
                 <source>This is not a valid UUID.</source>
-                <target>Deze waarde is geen geldige UUID waarde.</target>
+                <target>Dit is geen geldige UUID.</target>
             </trans-unit>
         </body>
     </file>