Update /certified paths to favor pretty links

Redirect search ?category=<category-name> to /<category-name> except
when multiple categories are selected.

redirects.yaml

@@ -124,15 +124,15 @@ category/product/(server|ubuntu-server-edition)/?: /server
 category/product/ubuntu-advantage/?: /support
 category/product/ubuntu-light/?: http://lubuntu.net/
 # old certification.ubuntu.com redirects
-certified/desktop/?: "/certified?category=Desktop&category=Laptop"
-certified/server/?: "/certified?category=Server"
-certified/soc/?: "/certified?category=SoC"
+certified/desktop/?: "/certified/desktops"
+certified/server/?: "/certified/servers"
+certified/soc/?: "/certified/socs"
 certified/hardware/(?P<canonical_id>.*): "/certified/{canonical_id}"
 certified/catalog/search/?: "/certified"
-certified/desktop/models/?: "/certified?category=Desktop&category=Laptop"
-certified/server/models/?: "/certified?category=Server"
+certified/desktop/models/?: "/certified/desktops"
+certified/server/models/?: "/certified/servers"
 certified/iot/models/?: "/certified/iot"
-certified/soc/models/?: "/certified?category=SoC"
+certified/soc/models/?: "/certified/socs"
 certified/why-certified/?: "/certified/why-certify"
 certified/devices/?: "/certified/iot"
 certification/?: "/certified"