Revert "Rename experiment to FeedSendFeedback."

This reverts commit 781b45f9.

Reason for revert: It seems that the experiment name needs to match the flag name, so we'll revert the experiment name change, and instead change the experiment name that we use on the Finch side.

Original change's description:
> Rename experiment to FeedSendFeedback.
> 
> The experiment name needs to match finch instead of matching the
> name of the flag we use in chromium.
> 
> Bug: 1045246
> Change-Id: Ie64379eb275d3a0c51c9d3237d9e12602003cc8a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2117914
> Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
> Reviewed-by: Dan H <harringtond@chromium.org>
> Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#753222}

TBR=petewil@chromium.org,asvitkine@chromium.org,harringtond@chromium.org

Change-Id: I37cb062deda3f30f457300a9b7bf4437c75475af
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1045246
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2121496Reviewed-by: Peter Williamson <petewil@chromium.org>
Commit-Queue: Peter Williamson <petewil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753428}

testing/variations/fieldtrial_testing_config.json

@@ -2300,21 +2300,6 @@
             ]
         }
     ],
-    "FeedSendFeedback": [
-        {
-            "platforms": [
-                "android"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "InterestFeedFeedback"
-                    ]
-                }
-            ]
-        }
-    ],
     "FilterAdsOnAbusiveSites": [
         {
             "platforms": [
@@ -2948,6 +2933,21 @@
             ]
         }
     ],
+    "InterestFeedFeedback": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "InterestFeedFeedback"
+                    ]
+                }
+            ]
+        }
+    ],
     "IsolatePasswordSites": [
         {
             "platforms": [