[Remote suggestions] Add a remote suggestions flag to choose the source

components/ntp_snippets/features.cc

Index: components/ntp_snippets/features.cc
diff --git a/components/ntp_snippets/features.cc b/components/ntp_snippets/features.cc
index 85b325f5f3e62ef27b622b45b784bb7796a1f5bc..c0a01e61cee9d1aaced761f23643cb6000bf44b8 100644
--- a/components/ntp_snippets/features.cc
+++ b/components/ntp_snippets/features.cc
@@ -34,9 +34,6 @@ const base::Feature kIncreasedVisibility{
 const base::Feature kPhysicalWebPageSuggestionsFeature{
     "NTPPhysicalWebPageSuggestions", base::FEATURE_ENABLED_BY_DEFAULT};
 
-const base::Feature kContentSuggestionsSource{
-    "NTPSnippets", base::FEATURE_ENABLED_BY_DEFAULT};
-
 const base::Feature kForeignSessionsSuggestionsFeature{
     "NTPForeignSessionsSuggestions", base::FEATURE_DISABLED_BY_DEFAULT};