[ntp] Disable most likely on desktop by default

Most likely has already been disabled on mobile and an experiment found
that most likely can also safely be disabled on desktop.

+ Remove now redundent fieltrial testing config of the desktop
  experiment.

Bug: 1009579
Change-Id: I5028c2babcef71862096dcd9684eaa29d0ad08b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2142758Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Steven Holte <holte@chromium.org>
Auto-Submit: Tibor Goldschwendt <tiborg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758247}

components/ntp_tiles/features.cc

@@ -21,15 +21,7 @@ const base::Feature kNtpMostLikelyFaviconsFromServerFeature{
 const base::Feature kUsePopularSitesSuggestions{
     "UsePopularSitesSuggestions", base::FEATURE_ENABLED_BY_DEFAULT};
 
-const base::FeatureState kDisplaySuggestionsServiceTilesDefaultState =
-#if defined(OS_ANDROID) || defined(OS_IOS)
-    base::FEATURE_DISABLED_BY_DEFAULT;
-#else
-    base::FEATURE_ENABLED_BY_DEFAULT;
-#endif
-
 const base::Feature kDisplaySuggestionsServiceTiles{
-    "DisplaySuggestionsServiceTiles",
-    kDisplaySuggestionsServiceTilesDefaultState};
+    "DisplaySuggestionsServiceTiles", base::FEATURE_DISABLED_BY_DEFAULT};
 
 }  // namespace ntp_tiles

testing/variations/fieldtrial_testing_config.json

@@ -3329,24 +3329,6 @@
             ]
         }
     ],
-    "MostLikelyDesktopDeprecation": [
-        {
-            "platforms": [
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Disabled",
-                    "disable_features": [
-                        "DisplaySuggestionsServiceTiles"
-                    ]
-                }
-            ]
-        }
-    ],
     "MyChromeEverywhere": [
         {
             "platforms": [