DOC: fix a typo for a "deviceatlas" keyword

The global keyword 'deviceatlas-properties-cookie' was miswritten.

This typo should also be backported to the 1.6 branch.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 9588759..78461f1 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -666,7 +666,7 @@
   Sets the character separator for the API properties results. This directive
   is optional and set to | by default if not set.
 
-devicatlas-properties-cookie <name>
+deviceatlas-properties-cookie <name>
   Sets the client cookie's name used for the detection if the DeviceAtlas
   Client-side component was used during the request. This directive is optional
   and set to DAPROPS by default if not set.