[fenix] Fixes https://github.com/mozilla-mobile/fenix/issues/5438 - Upgrade UI test devices to prevent slowdowns in test lab (https://github.com/mozilla-mobile/fenix/pull/5439)

* Fixes https://github.com/mozilla-mobile/fenix/issues/5438 - Upgrade UI test devices to prevent slowdowns in test lab

* fix: change api to supported version

* refactor: try x86 devices instead

automation/taskcluster/androidTest/flank-arm64-v8a.yml

@@ -34,9 +34,9 @@ gcloud:
   performance-metrics: true
 
   device:
-   - model: sailfish 
-     version: 25
-   - model: sailfish 
+   - model: walleye 
+     version: 26
+   - model: walleye 
      version: 28
 
 flank:

automation/taskcluster/lib/tasks.py

@@ -196,8 +196,7 @@ class TaskBuilder(object):
         )
 
         test_commands = (
-            'automation/taskcluster/androidTest/ui-test.sh arm64-v8a -1',
-            'automation/taskcluster/androidTest/ui-test.sh armeabi-v7a -1',
+            'automation/taskcluster/androidTest/ui-test.sh x86_64 -1',
         )
 
         command = ' && '.join(