Removed extra double quote

Author: Bunkermaster

Book/php7/internal_types/zvals/basic_structure.rst

@@ -303,7 +303,7 @@ read and to write the respective values. As an example consider the following fu
 
     PHP_FUNCTION(hello_world) {
         Z_TYPE_P(return_value) = IS_STRING;
-        Z_STR_P(return_value) = zend_string_init("hello world!", strlen(""hello world!"), 0);
+        Z_STR_P(return_value) = zend_string_init("hello world!", strlen("hello world!"), 0);
     };
 
     /* ... */