Rename didcot test case metadata name

This will allow the didcot test case page to be included in the test
case index page and test report page.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

test-cases/didcot.yaml

 metadata:
-  name: didcot-service
+  name: didcot
   format: "Apertis Test Definition 1.0"
   image-types:
     target:  [ armhf-internal, amd64 ]