Add AlwaysAllowJustInTimePaymentApp experiment to field trial test config.

Finch config CL: https://critique.corp.google.com/#review/262012910

Bug: 991381
Change-Id: Ie2da3a72a7f00c0f9de194b57d03cc7373ecd58b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1740506
Commit-Queue: Steven Holte <holte@chromium.org>
Auto-Submit: Danyao Wang <danyao@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685409}

testing/variations/fieldtrial_testing_config.json

@@ -3916,6 +3916,25 @@
             ]
         }
     ],
+    "PaymentRequestAlwaysAllowJustInTimePaymentApp": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "AlwaysAllowJustInTimePaymentApp"
+                    ]
+                }
+            ]
+        }
+    ],
     "PaymentRequestNoCreditCardAbort": [
         {
             "platforms": [