Add missing header

WardBrian · WardBrian · commit a0d4a7523458 · 2022-09-22T12:35:11.000-04:00
diff --git a/stan/math/prim/fun/conj.hpp b/stan/math/prim/fun/conj.hpp
@@ -2,6 +2,7 @@
 #define STAN_MATH_PRIM_FUN_CONJ_HPP
 
 #include <complex>
+#include <stan/math/prim/meta.hpp>
 
 namespace stan {
 namespace math {
