Rename both As{Byte,Wide}StringC() helpers to AsStringC().

The naming is redundant given the base type, and will stand
in the way of consolidating Byte and Wide code.

BUG=

Review URL: https://codereview.chromium.org/1862123003
diff --git a/fpdfsdk/javascript/Document.cpp b/fpdfsdk/javascript/Document.cpp
index 75cd2ec..4c361b1 100644
--- a/fpdfsdk/javascript/Document.cpp
+++ b/fpdfsdk/javascript/Document.cpp
@@ -784,7 +784,7 @@
     for (const auto& it : *pDictionary) {
       const CFX_ByteString& bsKey = it.first;
       CPDF_Object* pValueObj = it.second;
-      CFX_WideString wsKey = CFX_WideString::FromUTF8(bsKey.AsByteStringC());
+      CFX_WideString wsKey = CFX_WideString::FromUTF8(bsKey.AsStringC());
       if (pValueObj->IsString() || pValueObj->IsName()) {
         FXJS_PutObjectString(isolate, pObj, wsKey.c_str(),
                              pValueObj->GetUnicodeText().c_str());