make issue #508 test fail (as expected) (#522)

Just tweak the description for the GPS device so its hash changes, and
hence the order of the `GPS` and `Tardis` entities in a `Set Entity`
of devices that provide the `senseloc` capability.  When `GPS` comes
first, it will be chosen to provide the capability instead of
`Tardis`.

data/scenarios/Testing/508-capability-subset.yaml

@@ -47,7 +47,7 @@ entities:
       attr: water
       char: 'G'
     description:
-    - Satellite navigation device.
+    - A satellite navigation device.
     properties: [known, portable]
     capabilities: [senseloc]
   - name: Tardis

test/integration/Main.hs

@@ -161,7 +161,8 @@ testScenarioSolution _ci _em =
             assertBool "Robot 1 should not be in waiting set" $ not waiting
         , testSolution Default "Testing/490-harvest"
         , testSolution Default "Testing/504-teleport-self"
-        , testSolution Default "Testing/508-capability-subset.yaml"
+        , expectFailBecause "Awaiting fix (#508)" $
+            testSolution Default "Testing/508-capability-subset.yaml"
         ]
     ]
  where