[fix] robot test engine names

searx/settings_robot.yml

     useragent_suffix : ""
 
 engines:
-  - name : general_dummy
+  - name : general dummy
     engine : dummy
     categories : general
     shortcut : gd
 
-  - name : dummy_dummy
+  - name : dummy dummy
     engine : dummy
     categories : dummy
     shortcut : dd