Remove not used fields from XSTR

parse.y

@@ -11877,8 +11877,6 @@ rb_node_xstr_new(struct parser_params *p, VALUE nd_lit, const YYLTYPE *loc)
 {
     rb_node_xstr_t *n = NODE_NEWNODE(NODE_XSTR, rb_node_xstr_t, loc);
     n->nd_lit = nd_lit;
-    n->not_used = 0;
-    n->not_used2 = 0;
 
     return n;
 }

rubyparser.h

@@ -638,8 +638,6 @@ typedef struct RNode_XSTR {
     NODE node;
 
     VALUE nd_lit;
-    VALUE not_used;
-    VALUE not_used2;
 } rb_node_xstr_t;
 
 typedef struct RNode_DXSTR {