Format with c++23 standard

Follow-up to https://gn-review.googlesource.com/c/gn/+/22481. Now
that the clang-format CIPD package was updated to include the change
below, this can be landed.

https://github.com/llvm/llvm-project/commit/2ed87bad858138f5614bfb30670a47d1f779c76f

Change-Id: I8ef68ba1805940763960f969c8e27873b49bc0f7
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/22580
Commit-Queue: Victor Vianna <victorvianna@google.com>
Reviewed-by: Takuto Ikuta <tikuta@google.com>
diff --git a/.clang-format b/.clang-format
index e1aed24..e45f204 100644
--- a/.clang-format
+++ b/.clang-format
@@ -1,2 +1,2 @@
 BasedOnStyle: Chromium
-Standard: c++20
+Standard: c++23