Revert "[NTP][RQ] Adds field trial testing config for repeatable queries"

This reverts commit 4c19ca70.

Reason for revert: Broke NTP tests on MSan bots, see https://ci.chromium.org/ui/p/chromium/builders/ci/Linux%20MSan%20Tests/26482/test-results?expected=false&exonerated=true&flaky=true

Original change's description:
> [NTP][RQ] Adds field trial testing config for repeatable queries
>
> This is in preparation to promote the canary experiment which
> originally landed in cl/339288320 to Beta.
>
> Fixed: 1155314
> Change-Id: I4b87b89736e4cb461d416aacef98ed888596568c
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2573130
> Commit-Queue: Moe Ahmadi <mahmadi@chromium.org>
> Reviewed-by: Weilun Shi <sweilun@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#833576}

TBR=mahmadi@chromium.org,sweilun@chromium.org,chromium-scoped@luci-project-accounts.iam.gserviceaccount.com

Change-Id: I2f53745425e4df57bae943cbd3a4ab3c23de8cda
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2575340Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833796}

components/ntp_tiles/most_visited_sites.cc

@@ -401,9 +401,10 @@ void MostVisitedSites::AddOrRemoveBlockedUrl(const GURL& url, bool add_url) {
   }
 
   if (repeatable_queries_) {
-    // Restoring repeatable queries is not supported as deletion is permanent.
     if (add_url)
       repeatable_queries_->DeleteQueryWithDestinationURL(url);
+    else
+      NOTREACHED() << "Deleted repeatable queries cannot be restored.";
   }
 
   if (top_sites_) {

testing/variations/fieldtrial_testing_config.json

@@ -4632,30 +4632,6 @@
             ]
         }
     ],
-    "NtpRepeatableQueriesDesktop": [
-        {
-            "platforms": [
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "params": {
-                        "NtpRepeatableQueriesAgeThresholdDays": "180",
-                        "NtpRepeatableQueriesFrequencyExponent": "2",
-                        "NtpRepeatableQueriesInsertPosition": "start",
-                        "NtpRepeatableQueriesRecencyHalfLifeSeconds": "604800"
-                    },
-                    "enable_features": [
-                        "NtpRepeatableQueries"
-                    ]
-                }
-            ]
-        }
-    ],
     "NtpWebUIDesktop": [
         {
             "platforms": [