[ntp] Add testing config for MostLikelyDesktopDeprecation experiment

Bug: 1009579
Change-Id: I05870155fdba4e6c4fb2053661efebd3418017ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031555
Auto-Submit: Tibor Goldschwendt <tiborg@chromium.org>
Commit-Queue: Steven Holte <holte@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737856}

testing/variations/fieldtrial_testing_config.json

@@ -3709,6 +3709,24 @@
             ]
         }
     ],
+    "MostLikelyDesktopDeprecation": [
+        {
+            "platforms": [
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Disabled",
+                    "disable_features": [
+                        "DisplaySuggestionsServiceTiles"
+                    ]
+                }
+            ]
+        }
+    ],
     "MyChromeEverywhere": [
         {
             "platforms": [