Cleanup: Remove for_search param from search::InstantExtendedEnabledParam()

components/search/search.h

Index: components/search/search.h
diff --git a/components/search/search.h b/components/search/search.h
index 8969e81d0e02c373e17e89791fdefb603e104206..fa2b15c21b4e5828e7c3d1a6fa4b4f22aaecac58 100644
--- a/components/search/search.h
+++ b/components/search/search.h
@@ -58,11 +58,7 @@ bool GetBoolValueForFlagWithDefault(const std::string& flag,
 
 // Returns a string indicating whether InstantExtended is enabled, suitable
 // for adding as a query string param to the homepage or search requests.
-// Returns an empty string otherwise.
-//
-// |for_search| should be set to true for search requests, in which case this
-// returns a non-empty string only if query extraction is enabled.
-std::string InstantExtendedEnabledParam(bool for_search);
+std::string InstantExtendedEnabledParam();
 
 // Returns a string that will cause the search results page to update
 // incrementally. Currently, Instant Extended passes a different param to