[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 49c209742d3e7eadc14adabf5e6851712c052f64..b2f226409f17b0e443fc204279f1428482c5fa4e 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_DISABLED_BY_DEFAULT};
 
-const base::Feature kContentSuggestionsSource{
-    "NTPSnippets", base::FEATURE_ENABLED_BY_DEFAULT};
-
 const base::Feature kForeignSessionsSuggestionsFeature{
     "NTPForeignSessionsSuggestions", base::FEATURE_DISABLED_BY_DEFAULT};