Remove stray CFXJSE_Value forward declaration from ijs_runtime.h

Don't pollute the non-XFA code with an XFA-only type. It is not
required here.

Change-Id: Iaf8b6b97182011f53b635ec826e23db9b346ddd7
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/65970
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

fxjs/ijs_runtime.h

diff --git a/fxjs/ijs_runtime.h b/fxjs/ijs_runtime.h
index ca103aa..b61eca8 100644
--- a/fxjs/ijs_runtime.h
+++ b/fxjs/ijs_runtime.h
@@ -14,7 +14,6 @@
 #include "core/fxcrt/unowned_ptr.h"
 #include "third_party/base/optional.h"
 
-class CFXJSE_Value;
 class CJS_Runtime;
 class CPDFSDK_FormFillEnvironment;
 class IJS_EventContext;