[ios] Launch location permissions experiment to 45% in Stable

Since this is a client-side driven experiment, the client must
turn it on to 45% stable.

Bug: 1138603
Change-Id: Ibe97fd2b7f92e19e3461ad635bbce9b5f6ee94a2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2588301Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Auto-Submit: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840649}

ios/chrome/browser/ui/first_run/location_permissions_field_trial.cc

@@ -87,11 +87,10 @@ int CreateFirstRunTrial(
       default_percent = 1;
       break;
     case version_info::Channel::STABLE:
-      // Disabled on stable pending approval. https://crbug.com/1126969
-      fre_modal_enabled_percent = 0;
-      remove_fre_prompt_enabled_percent = 0;
-      disabled_percent = 0;
-      default_percent = 100;
+      fre_modal_enabled_percent = 15;
+      remove_fre_prompt_enabled_percent = 15;
+      disabled_percent = 15;
+      default_percent = 55;
       break;
   }