Clarify two more comments (#2384)

* Make language clearer

* Two more comments

libafl/src/common/nautilus/grammartec/tree.rs

@@ -280,7 +280,8 @@ impl Tree {
         for i in 0..self.size() {
             let node_id = NodeId::from(i);
             let nonterm = self.get_rule(node_id, ctx).nonterm();
-            //sanity check
+
+            // This should never panic!
             let (nterm_id, node) = stack.pop().expect("Not a valid tree for unparsing!");
             if nterm_id == nonterm {
                 self.paren[i] = node;

libafl/src/feedbacks/map.rs

@@ -822,7 +822,7 @@ mod tests {
 
     #[test]
     fn test_map_is_novel() {
-        // sanity check
+        // This should always hold
         assert!(AllIsNovel::is_novel(0_u8, 0));
 
         assert!(!NextPow2IsNovel::is_novel(0_u8, 0));