Remove duplicate widestring literals from CXFA_*.cpp classes

We have the equivalent narrow string in the element.inc table.
Widen the string as needed in a few spots.

Change-Id: I303d2cadff6144b80fda778c0aeacc627ad730af
Reviewed-on: https://pdfium-review.googlesource.com/c/47131
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

xfa/fxfa/parser/cxfa_documentassembly.cpp

diff --git a/xfa/fxfa/parser/cxfa_documentassembly.cpp b/xfa/fxfa/parser/cxfa_documentassembly.cpp
index f3cbc34..ee83ef4 100644
--- a/xfa/fxfa/parser/cxfa_documentassembly.cpp
+++ b/xfa/fxfa/parser/cxfa_documentassembly.cpp
@@ -13,8 +13,6 @@
     {XFA_Attribute::Lock, XFA_AttributeType::Integer, (void*)0},
     {XFA_Attribute::Unknown, XFA_AttributeType::Integer, nullptr}};
 
-constexpr wchar_t kDocumentAssemblyName[] = L"documentAssembly";
-
 }  // namespace
 
 CXFA_DocumentAssembly::CXFA_DocumentAssembly(CXFA_Document* doc,
@@ -25,7 +23,6 @@
                 XFA_ObjectType::ContentNode,
                 XFA_Element::DocumentAssembly,
                 nullptr,
-                kDocumentAssemblyAttributeData,
-                kDocumentAssemblyName) {}
+                kDocumentAssemblyAttributeData) {}
 
-CXFA_DocumentAssembly::~CXFA_DocumentAssembly() {}
+CXFA_DocumentAssembly::~CXFA_DocumentAssembly() = default;