Use DCHECK_IS_ON() in cfx_char.cpp.

Fix the build for release builds with DCHECK_ALWAYS_ON after
https://pdfium-review.googlesource.com/74395 landed.

Tbr: tsepez@chromium.org
Bug: pdfium:1596
Change-Id: Ic0dfcc944fc087c16e621ab86f3ab96d944b8cdb
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/74551
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

xfa/fgas/layout/cfx_char.cpp

diff --git a/xfa/fgas/layout/cfx_char.cpp b/xfa/fgas/layout/cfx_char.cpp
index 0782bd3..6c600ae 100644
--- a/xfa/fgas/layout/cfx_char.cpp
+++ b/xfa/fgas/layout/cfx_char.cpp
@@ -14,9 +14,9 @@
 
 namespace {
 
-#ifndef NDEBUG
+#if DCHECK_IS_ON()
 constexpr int32_t kBidiMaxLevel = 61;
-#endif  // NDEBUG
+#endif
 
 #undef PACK_NIBBLES
 #define PACK_NIBBLES(hi, lo) \