Fix broadcast logic

Author: andrjohns

stan/math/prim/prob/bernoulli_lccdf.hpp

@@ -55,7 +55,7 @@ return_type_t<T_prob> bernoulli_lccdf(const T_n& n, const T_prob& theta) {
 
   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);
+  double broadcast_n = theta_size == n_size ? 1 : n_size;
 
   if (!is_constant_all<T_prob>::value) {
     partials<0>(ops_partials) = inv(theta_arr) * broadcast_n;