[regexp] Fix gcc link error for RegExpClassSetExpression::Empty

Fix gcc link error by adding missing include.

Change-Id: I95fcd09ad6c89d1b3d38c3f31a2cfad8ff464701
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4224459
Commit-Queue: Patrick Thier <pthier@chromium.org>
Auto-Submit: Patrick Thier <pthier@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#85691}

src/regexp/regexp-ast.cc

@@ -3,7 +3,9 @@
 // found in the LICENSE file.
 
 #include "src/regexp/regexp-ast.h"
+
 #include "src/utils/ostreams.h"
+#include "src/zone/zone-list-inl.h"
 
 namespace v8 {
 namespace internal {