Don't leak the env_vars_sorted smartlist in process_environment_make

Found by Coverity.

No changes/ file, because this bug has not been in a release yet.

src/common/util.c

@@ -3823,6 +3823,8 @@ process_environment_make(struct smartlist_t *env_vars)
     tor_assert(cp == env->windows_environment_block + total_env_length - 1);
   }
 
+  smartlist_free(env_vars_sorted);
+
   return env;
 }