Bug 1800926 - adjust screen resolution for win gpu instances to be more compatible. r=bxbrenden

Differential Revision: https://phabricator.services.mozilla.com/D162222

testing/mozharness/external_tools/machine-configuration.json

@@ -22,7 +22,7 @@
     "win10-vm": {
         "screen_resolution": {
             "x": 2560,
-            "y": 1600
+            "y": 1440
         },
         "mouse_position": {
             "x": 1010,