Add testing variation for WebPageTextAccessibility

Bug: none
Change-Id: Ib0451376274be225950222dcaba6b7a63e0b5d86
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2106168Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Robbie Gibson <rkgibson@google.com>
Cr-Commit-Position: refs/heads/master@{#752826}

testing/variations/fieldtrial_testing_config.json

@@ -2656,6 +2656,21 @@
             ]
         }
     ],
+    "IOSWebPageTextAccessibility": [
+        {
+            "platforms": [
+                "ios"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "WebPageTextAccessibility"
+                    ]
+                }
+            ]
+        }
+    ],
     "IdentityDiscIPH": [
         {
             "platforms": [