Remove -Wno-pointer-to-int-cast from fxcodec target.

Presumably, a libopenjpeg upgrade fixed third_party/libopenjpeg20/mct.c.

Change-Id: I0e0e593b0cf7f32934ce45b19a54fe556b955448
Reviewed-on: https://pdfium-review.googlesource.com/39411
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index 24dfd1d..afa83e3 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -827,11 +827,6 @@
       deps += [ "third_party:fx_tiff" ]
     }
   }
-  if (is_posix || is_fuchsia) {
-    # core/fxcodec/fx_libopenjpeg/src/fx_mct.c does an pointer-to-int
-    # conversion to check that an address is 16-bit aligned (benign).
-    cflags_c = [ "-Wno-pointer-to-int-cast" ]
-  }
 }
 
 config("fxge_warnings") {