Revert of Make extensions DSE persistent in browser prefs

components/search_engines/BUILD.gn

Index: components/search_engines/BUILD.gn
diff --git a/components/search_engines/BUILD.gn b/components/search_engines/BUILD.gn
index fe5b1d483c0f97479a1af8fc5f6a85ff3e405b8c..cf7293bc938b9a9b786ce78a5802a817308b470c 100644
--- a/components/search_engines/BUILD.gn
+++ b/components/search_engines/BUILD.gn
@@ -98,8 +98,6 @@
 static_library("test_support") {
   testonly = true
   sources = [
-    "search_engines_test_util.cc",
-    "search_engines_test_util.h",
     "testing_search_terms_data.cc",
     "testing_search_terms_data.h",
   ]
@@ -107,7 +105,6 @@
   public_deps = [
     ":search_engines",
     "//base",
-    "//components/sync_preferences:test_support",
     "//testing/gtest",
   ]
 }