Rollup merge of #154029 - xtqqczze:clear, r=joboet

Replace `truncate(0)` with `clear()`

compiler/rustc_data_structures/src/obligation_forest/mod.rs

@@ -702,7 +702,7 @@ fn compress(&mut self, mut outcome_cb: impl FnMut(&O)) {
             self.apply_rewrites(&node_rewrites);
         }
 
-        node_rewrites.truncate(0);
+        node_rewrites.clear();
         self.reused_node_vec = node_rewrites;
     }