Remove not used fields from STR

parse.y

@@ -11849,8 +11849,6 @@ rb_node_str_new(struct parser_params *p, VALUE nd_lit, const YYLTYPE *loc)
 {
     rb_node_str_t *n = NODE_NEWNODE(NODE_STR, rb_node_str_t, loc);
     n->nd_lit = nd_lit;
-    n->not_used = 0;
-    n->not_used2 = 0;
 
     return n;
 }

rubyparser.h

@@ -618,8 +618,6 @@ typedef struct RNode_STR {
     NODE node;
 
     VALUE nd_lit;
-    VALUE not_used;
-    VALUE not_used2;
 } rb_node_str_t;
 
 /* RNode_DSTR, RNode_DXSTR and RNode_DSYM should be same structure */