Remove internal newlines in stansummary output

Author: WardBrian

src/cmdstan/stansummary_helper.hpp

@@ -687,13 +687,11 @@ void write_sampler_info(const stan::io::stan_csv_metadata &metadata,
   *out << prefix
        << "For each parameter, ESS_bulk and ESS_tail measure the "
           "effective sample size "
-       << std::endl
        << "for the entire sample (bulk) and for the "
           "the .05 and .95 tails (tail), "
        << std::endl;
   *out << prefix
        << "and R_hat measures the potential scale reduction on split chains."
-       << std::endl
        << "At convergence R_hat will be very close to 1.00." << std::endl;
 }