MM-54505: re-enable remote marketplace functionality (#24561)

server/channels/api4/system_test.go

@@ -855,8 +855,6 @@ func TestPushNotificationAck(t *testing.T) {
 }
 
 func TestCompleteOnboarding(t *testing.T) {
-	os.Setenv("MM_FEATUREFLAGS_STREAMLINEDMARKETPLACE", "false")
-	defer os.Unsetenv("MM_FEATUREFLAGS_STREAMLINEDMARKETPLACE")
 	th := Setup(t)
 	defer th.TearDown()