Revert "Re-enable clang VLA warning"

This reverts commit 4b05c17584.

Reason for revert: Causing compile failure in chrome/browser/ash/chromebox_for_meetings/xu_camera/xu_camera_service.cc

Original change's description:
> Re-enable clang VLA warning
>
> We've finally removed all uses of variable-length arrays from the Chromium codebase (see https://crbug.com/349656479), so we can re-enable clang's warning to ensure no further ones get added.
>
> Fixed: 349656479, 40286317
> Change-Id: I8d62b11c8e7c61ad6c955a9fe221b086706d127c
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5707850
> Reviewed-by: Hans Wennborg <hans@chromium.org>
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Commit-Queue: Devon Loehr <dloehr@google.com>
> Cr-Commit-Position: refs/heads/main@{#1354667}

Change-Id: I31868abb3a666101a56b37988518b7107c0f2339
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5854358
Reviewed-by: Chan Li <chanli@chromium.org>
Auto-Submit: Devon Loehr <dloehr@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Chan Li <chanli@chromium.org>
Owners-Override: Chan Li <chanli@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1354709}

build/config/compiler/BUILD.gn

@@ -1957,6 +1957,9 @@ config("default_warnings") {
         # TODO(crbug.com/40255410) Evaluate and possibly enable.
         "-Wno-deprecated-this-capture",
 
+        # TODO(crbug.com/40286317): Evaluate and possibly enable.
+        "-Wno-vla-extension",
+
         # TODO(crbug.com/40284799): Fix and re-enable.
         "-Wno-thread-safety-reference-return",
       ]