Header fixes

Author: WardBrian

stan/math/prim/constraint/sum_to_zero_constrain.hpp

@@ -3,7 +3,8 @@
 
 #include <stan/math/prim/meta.hpp>
 #include <stan/math/prim/fun/Eigen.hpp>
-#include <stan/math/prim/fun/sum.hpp>
+#include <stan/math/prim/fun/to_ref.hpp>
+#include <stan/math/prim/fun/inv_sqrt.hpp>
 #include <stan/math/prim/functor/apply_vector_unary.hpp>
 #include <cmath>
 

stan/math/prim/constraint/sum_to_zero_free.hpp

@@ -5,6 +5,7 @@
 #include <stan/math/prim/err.hpp>
 #include <stan/math/prim/fun/Eigen.hpp>
 #include <stan/math/prim/fun/to_ref.hpp>
+#include <stan/math/prim/fun/sqrt.hpp>
 #include <stan/math/prim/functor/apply_vector_unary.hpp>
 #include <cmath>
 

stan/math/rev/constraint/sum_to_zero_constrain.hpp

@@ -4,11 +4,9 @@
 #include <stan/math/rev/meta.hpp>
 #include <stan/math/rev/core/reverse_pass_callback.hpp>
 #include <stan/math/rev/core/arena_matrix.hpp>
-#include <stan/math/rev/fun/value_of.hpp>
 #include <stan/math/prim/fun/Eigen.hpp>
+#include <stan/math/prim/fun/sqrt.hpp>
 #include <stan/math/prim/constraint/sum_to_zero_constrain.hpp>
-#include <stan/math/prim/fun/linspaced_vector.hpp>
-#include <stan/math/prim/fun/cumulative_sum.hpp>
 #include <cmath>
 #include <tuple>
 #include <vector>