This fixes the following compiler warning:

```
src/compiler/backend/register-allocator-verifier.cc:365:19: warning: loop variable 'pair' of type 'const
      std::__1::pair<const v8::internal::compiler::InstructionOperand, v8::internal::compiler::Assessment *>' creates a
      copy from type 'const std::__1::pair<const v8::internal::compiler::InstructionOperand,
      v8::internal::compiler::Assessment *>' [-Wrange-loop-analysis]
  for (const auto pair : map()) {
                  ^
src/compiler/backend/register-allocator-verifier.cc:365:8: note: use reference type 'const
      std::__1::pair<const v8::internal::compiler::InstructionOperand, v8::internal::compiler::Assessment *> &' to
      prevent copying
  for (const auto pair : map()) {
       ^~~~~~~~~~~~~~~~~
                  &
```
Signed-off-by: Darshan Sen <raisinten@gmail.com>
Change-Id: Ifbaa85345d8dcdf56a68d194bba98d76878c96f3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3538286Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79555}