Update the docker image

.taskcluster.yml

diff --git a/.taskcluster.yml b/.taskcluster.yml
index b24b4f8..e6fbfbb 100644
--- a/.taskcluster.yml
+++ b/.taskcluster.yml
@@ -57,7 +57,7 @@
             owner: ${owner}
             source: ${event.repository.clone_url}
           payload:
-            image: webplatformtests/wpt:0.48
+            image: webplatformtests/wpt:0.51
             maxRunTime: 7200
             artifacts:
               public/results:

tools/ci/tc/tasks/test.yml

diff --git a/tools/ci/tc/tasks/test.yml b/tools/ci/tc/tasks/test.yml
index 85496dc..0a06a4b 100644
--- a/tools/ci/tc/tasks/test.yml
+++ b/tools/ci/tc/tasks/test.yml
@@ -4,7 +4,7 @@
     workerType: ci
     schedulerId: taskcluster-github
     deadline: "24 hours"
-    image: webplatformtests/wpt:0.48
+    image: webplatformtests/wpt:0.51
     maxRunTime: 7200
     artifacts:
       public/results: