[compiler] Don't copy blocks in `EnsureCFGWellFormedness`

This is no longer necessary, because `EnsureSplitEdgeForm` no longer
adds new blocks.

Change-Id: I48daaa556ff1be5c9641b054937699ac401613f9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3810464Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/main@{#82305}

src/compiler/schedule.cc

@@ -332,12 +332,8 @@ void Schedule::InsertSwitch(BasicBlock* block, BasicBlock* end, Node* sw,
 }
 
 void Schedule::EnsureCFGWellFormedness() {
-  // Make a copy of all the blocks for the iteration, since adding the split
-  // edges will allocate new blocks.
-  BasicBlockVector all_blocks_copy(all_blocks_);
-
-  // Insert missing split edge blocks.
-  for (BasicBlock* block : all_blocks_copy) {
+  // Ensure there are no critical edges.
+  for (BasicBlock* block : all_blocks_) {
     if (block->PredecessorCount() > 1) {
       if (block != end_) {
         EnsureSplitEdgeForm(block);