Fix duplicated mustache section close

Summary: There are two `{{/function:stream?}}` here

Reviewed By: yfeldblum, yoney

Differential Revision: D60682630

fbshipit-source-id: 9353b1b9af5764ced2b244f80e92e59569b9813f

thrift/compiler/generate/templates/cpp2/metadata/return_type_gen.mustache

@@ -17,5 +17,5 @@
 }}{{^function:sink?}}{{ > metadata/type_gen }}{{/function:sink?}}{{!
 }}{{#function:sink?}}std::make_unique<Sink>({{#function:sink_elem_type}}{{ > metadata/type_gen}}{{/function:sink_elem_type}}, {{#function:sink_final_response_type}}{{ > metadata/type_gen}}{{/function:sink_final_response_type}}{{#function:sink_has_first_response?}}, {{#function:sink_first_response_type}}{{ > metadata/type_gen}}{{/function:sink_first_response_type}}{{/function:sink_has_first_response?}}){{/function:sink?}}{{!
 }}{{#function:stream?}}{{!
-}}std::make_unique<Stream>({{#function:stream_elem_type}}{{ > metadata/type_gen}}{{/function:stream_elem_type}}{{#function:stream_has_first_response?}}, {{#function:stream_first_response_type}}{{ > metadata/type_gen}}{{/function:stream_first_response_type}}{{/function:stream_has_first_response?}}){{/function:stream?}}{{!
+}}std::make_unique<Stream>({{#function:stream_elem_type}}{{ > metadata/type_gen}}{{/function:stream_elem_type}}{{#function:stream_has_first_response?}}, {{#function:stream_first_response_type}}{{ > metadata/type_gen}}{{/function:stream_first_response_type}}{{/function:stream_has_first_response?}}){{!
 }}{{/function:stream?}}