Clean up D3D11VideoDecoder experiment names

Cleaning up the field trial config here: cl/341906454

Change-Id: I8082c282de63c441e5c6c8e3875f365b1f295571
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2535628Reviewed-by: Weilun Shi <sweilun@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827382}

testing/variations/fieldtrial_testing_config.json

@@ -1996,18 +1996,17 @@
             ]
         }
     ],
-    "D3D11VideoDecoderStable": [
+    "D3D11VideoDecoder": [
         {
             "platforms": [
                 "windows"
             ],
             "experiments": [
                 {
-                    "name": "D3D11StableEnabledV2",
+                    "name": "Enabled",
                     "enable_features": [
                         "D3D11VideoDecoder",
-                        "D3D11VideoDecoderCopyPictures",
-                        "D3D11VideoDecoderLimitTo11_0"
+                        "D3D11VideoDecoderCopyPictures"
                     ]
                 }
             ]