Fix warning for finch config of TranslateCompactUI_Stable.

CL/179034570 asked for adding an entry for my experiment group. This
change should resolve it.

TBR=isherman@chromium.org

Change-Id: I30de06b41f5266635cf2cab3b1710702cc9811af
Reviewed-on: https://chromium-review.googlesource.com/831003Reviewed-by: Leo Zhang <googleo@chromium.org>
Commit-Queue: Leo Zhang <googleo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524683}

testing/variations/fieldtrial_testing_config.json

@@ -3748,9 +3748,9 @@
             ],
             "experiments": [
                 {
-                    "name": "NeverThresholdEquals7",
+                    "name": "DarkerColor",
                     "params": {
-                        "translate_auto_never_threshold": "7"
+                        "translate_tab_default_text_color": "1"
                     },
                     "enable_features": [
                         "TranslateCompactUI"