Remove select broadcast hack

Author: andrjohns

stan/math/prim/prob/bernoulli_lccdf.hpp

@@ -53,12 +53,15 @@ return_type_t<T_prob> bernoulli_lccdf(const T_n& n, const T_prob& theta) {
     return ops_partials.build(NEGATIVE_INFTY);
   }
 
-  // Use select() to broadcast theta values & gradients if necessary
+  size_t theta_size = math::size(theta_arr);
+  size_t n_size = math::size(n_arr);
+  double broadcast_n = theta_size == n_size ? 1 : std::fmax(theta_size, n_size);
+
   if (!is_constant_all<T_prob>::value) {
-    partials<0>(ops_partials) = select(true, inv(theta_arr), n_arr);
+    partials<0>(ops_partials) = inv(theta_arr) * broadcast_n;
   }
 
-  return ops_partials.build(sum(select(true, log(theta_arr), n_arr)));
+  return ops_partials.build(sum(log(theta_arr)) * broadcast_n);
 }
 
 }  // namespace math